diff --git a/lib/grade/grade_calculation.php b/lib/grade/grade_calculation.php
index beb786962fb..1508dc89a21 100644
--- a/lib/grade/grade_calculation.php
+++ b/lib/grade/grade_calculation.php
@@ -91,14 +91,15 @@ class grade_calculation extends grade_object {
      */
     function fetch($field1, $value1, $field2='', $value2='', $field3='', $value3='', $fields="*") { 
         if ($grade_calculation = get_record('grade_calculations', $field1, $value1, $field2, $value2, $field3, $value3, $fields)) {
-            if (!isset($this)) {
-                $grade_calculation = new grade_calculation($grade_calculation);
-                return $grade_calculation;
-            } else {
+            if (isset($this) && get_class($this) == 'grade_calculation') {
+                print_object($this);
                 foreach ($grade_calculation as $param => $value) {
                     $this->$param = $value;
                 }
                 return $this;
+            } else {
+                $grade_calculation = new grade_calculation($grade_calculation);
+                return $grade_calculation;
             }
         } else {
             return false;
diff --git a/lib/grade/grade_category.php b/lib/grade/grade_category.php
index f5af8674376..9b34efd2047 100644
--- a/lib/grade/grade_category.php
+++ b/lib/grade/grade_category.php
@@ -27,7 +27,7 @@ require_once('grade_object.php');
 
 class grade_category extends grade_object {
     /**
-     * DB Table (used by grade_object).
+     * The DB table.
      * @var string $table
      */
     var $table = 'grade_categories';
@@ -36,7 +36,7 @@ class grade_category extends grade_object {
      * Array of class variables that are not part of the DB table fields
      * @var array $nonfields
      */
-    var $nonfields = array('table', 'nonfields');
+    var $nonfields = array('table', 'nonfields', 'children', 'all_children');
     
     /**
      * The course this category belongs to.
@@ -99,6 +99,13 @@ class grade_category extends grade_object {
      */
     var $children;
 
+    /**
+     * A hierarchical array of all children below this category. This is stored separately from 
+     * $children because it is more memory-intensive and may not be used as often.
+     * @var array $all_children
+     */
+    var $all_children;
+
     /**
      * Constructor. Extends the basic functionality defined in grade_object.
      * @param array $params Can also be a standard object.
@@ -144,14 +151,14 @@ class grade_category extends grade_object {
     function fetch($field1, $value1, $field2='', $value2='', $field3='', $value3='', $fields="*")
     { 
         if ($grade_category = get_record('grade_categories', $field1, $value1, $field2, $value2, $field3, $value3, $fields)) {
-            if (!isset($this)) {
-                $grade_category = new grade_category($grade_category);
-                return $grade_category;
-            } else {
+            if (isset($this) && get_class($this) == 'grade_category') {
                 foreach ($grade_category as $param => $value) {
                     $this->$param = $value;
                 }
                 return $this;
+            } else {
+                $grade_category = new grade_category($grade_category);
+                return $grade_category;
             }
         } else {
             return false;
@@ -195,6 +202,44 @@ class grade_category extends grade_object {
 
         return $depth;
     }
+
+    /**
+     * Fetches and returns all the children categories and/or grade_items belonging to this category. 
+     * By default only returns the immediate children (depth=1), but deeper levels can be requested, 
+     * as well as all levels (0).
+     * @param int $depth 1 for immediate children, 0 for all children, and 2+ for specific levels deeper than 1.
+     * @param string $arraytype Either 'nested' or 'flat'. A nested array represents the true hierarchy, but is more difficult to work with.
+     * @return array Array of child objects (grade_category and grade_item).
+     */
+    function get_children($depth=1, $arraytype='nested') {
+        $children = array();
+
+        if ($depth == 1) {
+            if (!empty($this->children)) {
+                return $this->children;
+            } else {
+                $cat = new grade_category();
+                $cat->parent = $this->id;
+                $children = $cat->fetch_all_using_this();
+                $item = new grade_item();
+                $item->categoryid = $this->id;
+                $item_children = $item->fetch_all_using_this();
+
+                if (!empty($children)) {                    
+                    $children = array_merge($children, $item_children);
+                } else {
+                    $children = $item_children;
+                }
+
+                $this->children = $children;
+            }
+        } elseif ($depth > 1) {
+            // TODO implement
+        } elseif ($depth == 0) {
+            // TODO implement
+        }
+        return $children;
+    }
 }
 
 ?>
diff --git a/lib/grade/grade_grades_final.php b/lib/grade/grade_grades_final.php
index 6ffd62b0e96..82c7958bd2a 100644
--- a/lib/grade/grade_grades_final.php
+++ b/lib/grade/grade_grades_final.php
@@ -27,7 +27,7 @@ require_once('grade_object.php');
 
 class grade_grades_final extends grade_object {
     /**
-     * DB Table (used by grade_object).
+     * The DB table.
      * @var string $table
      */
     var $table = 'grade_grades_final';
@@ -36,7 +36,7 @@ class grade_grades_final extends grade_object {
      * Array of class variables that are not part of the DB table fields
      * @var array $nonfields
      */
-    var $nonfields = array('table', 'nonfields');
+    var $nonfields = array('nonfields', 'table');
     
     /**
      * The id of the grade_item this final grade belongs to.
@@ -110,14 +110,14 @@ class grade_grades_final extends grade_object {
      */
     function fetch($field1, $value1, $field2='', $value2='', $field3='', $value3='', $fields="*") { 
         if ($object = get_record('grade_grades_final', $field1, $value1, $field2, $value2, $field3, $value3, $fields)) {
-            if (!isset($this)) {
-                $object = new grade_grades_final($object);
-                return $object;
-            } else {
+            if (isset($this) && get_class($this) == 'grade_grades_final') {
                 foreach ($object as $param => $value) {
                     $this->$param = $value;
                 }
                 return $this;
+            } else {
+                $object = new grade_grades_final($object);
+                return $object;
             }
         } else {
             return false;
diff --git a/lib/grade/grade_grades_raw.php b/lib/grade/grade_grades_raw.php
index 79216c3d98f..1d9d8b37e85 100644
--- a/lib/grade/grade_grades_raw.php
+++ b/lib/grade/grade_grades_raw.php
@@ -26,8 +26,9 @@
 require_once('grade_object.php');
 
 class grade_grades_raw extends grade_object {
+    
     /**
-     * DB Table (used by grade_object).
+     * The DB table.
      * @var string $table
      */
     var $table = 'grade_grades_raw';
@@ -121,14 +122,14 @@ class grade_grades_raw extends grade_object {
     function fetch($field1, $value1, $field2='', $value2='', $field3='', $value3='', $fields="*")
     { 
         if ($object = get_record('grade_grades_raw', $field1, $value1, $field2, $value2, $field3, $value3, $fields)) {
-            if (!isset($this)) {
-                $object = new grade_grades_raw($object);
-                return $object;
-            } else {
+            if (isset($this) && get_class($this) == 'grade_grades_raw') {
                 foreach ($object as $param => $value) {
                     $this->$param = $value;
                 }
                 return $this;
+            } else {
+                $object = new grade_grades_raw($object);
+                return $object;
             }
         } else {
             return false;
diff --git a/lib/grade/grade_item.php b/lib/grade/grade_item.php
index 00d865cf838..91561490e61 100644
--- a/lib/grade/grade_item.php
+++ b/lib/grade/grade_item.php
@@ -213,14 +213,14 @@ class grade_item extends grade_object {
      */
     function fetch($field1, $value1, $field2='', $value2='', $field3='', $value3='', $fields="*") { 
         if ($grade_item = get_record('grade_items', $field1, $value1, $field2, $value2, $field3, $value3, $fields)) {
-            if (!isset($this)) {
-                $grade_item = new grade_item($grade_item);
-                return $grade_item;
-            } else {
+            if (isset($this) && get_class($this) == 'grade_item') {
                 foreach ($grade_item as $param => $value) {
                     $this->$param = $value;
                 }
                 return $this;
+            } else {
+                $grade_item = new grade_item($grade_item);
+                return $grade_item;
             }
         } else {
             return false;
@@ -298,12 +298,11 @@ class grade_item extends grade_object {
      * @return mixed $calculation A string if found, false otherwise.
      */
     function get_calculation($fetch = false) {
-        if (!$fetch) {
+        if (!$fetch && get_class($this->calculation) == 'grade_calculation') {
             return $this->calculation;
         } 
-        
-        $grade_calculation = grade_calculation::fetch(true, 'itemid', $this->id);
-        
+        $grade_calculation = grade_calculation::fetch('itemid', $this->id);
+            
         if (empty($grade_calculation)) { // There is no calculation in DB
             return false;
         } elseif ($grade_calculation->calculation != $this->calculation->calculation) { // The object's calculation is not in sync with the DB (new value??)
diff --git a/lib/grade/grade_object.php b/lib/grade/grade_object.php
index ea203807bd0..02ed32cd8cf 100644
--- a/lib/grade/grade_object.php
+++ b/lib/grade/grade_object.php
@@ -132,7 +132,20 @@ class grade_object {
         // Trim trailing AND
         $wheresql = substr($wheresql, 0, strrpos($wheresql, 'AND'));
 
-        return get_records_select($this->table, $wheresql, 'id');
+        $objects = get_records_select($this->table, $wheresql, 'id');
+        
+        if (!empty($objects)) {
+            $full_objects = array();
+
+            // Convert the stdClass objects returned by the get_records_select method into proper objects
+            $classname = get_class($this);
+            foreach ($objects as $id => $stdobject) {
+                $full_objects[$id] = new $classname($stdobject, false);
+            }
+            return $full_objects;
+        } else {
+            return $objects;
+        }
     }
   
     /**
diff --git a/lib/simpletest/testgradelib.php b/lib/simpletest/testgradelib.php
index 6434306d32a..58ba8281534 100644
--- a/lib/simpletest/testgradelib.php
+++ b/lib/simpletest/testgradelib.php
@@ -51,6 +51,12 @@ delete_records_select('grade_items', 'itemname LIKE "%unittest%"');
 delete_records_select('grade_calculation', 'calculation LIKE "%unittest%"');
 delete_records_select('scale', 'name LIKE "%unittest%"');
 */
+
+/**
+ * Here is a brief explanation of the test data set up in these unit tests.
+ * category1 => array(grade_item1, grade_item3, category2 => array(grade_item2))
+ * 3 users for 3 grade_items
+ */
 class gradelib_test extends UnitTestCase {
    
     /**
@@ -129,6 +135,22 @@ class gradelib_test extends UnitTestCase {
         if ($grade_category->id = insert_record('grade_categories', $grade_category)) {
             $this->grade_categories[] = $grade_category;
         } 
+        
+        $grade_category = new stdClass();
+        
+        $grade_category->fullname    = 'unittestcategory2';
+        $grade_category->courseid    = $this->courseid;
+        $grade_category->aggregation = GRADE_AGGREGATE_MODE;
+        $grade_category->keephigh    = 100;
+        $grade_category->droplow     = 10;
+        $grade_category->hidden      = 0;
+        $grade_category->parent      = $this->grade_categories[0]->id;
+        $grade_category->timecreated = mktime();
+        $grade_category->timemodified = mktime();
+        
+        if ($grade_category->id = insert_record('grade_categories', $grade_category)) {
+            $this->grade_categories[] = $grade_category;
+        } 
     }
 
     /**
@@ -156,6 +178,7 @@ class gradelib_test extends UnitTestCase {
         $grade_item = new stdClass();
 
         $grade_item->courseid = $this->courseid;
+        $grade_item->categoryid = $this->grade_categories[1]->id;
         $grade_item->itemname = 'unittestgradeitem2';
         $grade_item->itemtype = 'import';
         $grade_item->itemmodule = 'assignment';
@@ -881,21 +904,66 @@ class gradelib_test extends UnitTestCase {
     }
 
     function test_grade_category_insert() {
+        $grade_category = new grade_category();
+        $this->assertTrue(method_exists($grade_category, 'insert'));
+        
+        $grade_category->fullname    = 'unittestcategory3';
+        $grade_category->courseid    = $this->courseid;
+        $grade_category->aggregation = GRADE_AGGREGATE_MODE;
+        $grade_category->keephigh    = 100;
+        $grade_category->droplow     = 10;
+        $grade_category->hidden      = 0;
+        $grade_category->parent      = $this->grade_categories[0]->id;
+
+        $grade_category->insert();
+
+        $last_grade_category = end($this->grade_categories);
+
+        $this->assertEqual($grade_category->id, $last_grade_category->id + 1);
+        $this->assertTrue(!empty($grade_category->timecreated));
+        $this->assertTrue(!empty($grade_category->timemodified));
+        $this->grade_categories[] = $grade_category; 
 
     }
 
     function test_grade_category_update() {
-
+        $grade_category = new grade_category($this->grade_categories[0]);
+        $this->assertTrue(method_exists($grade_category, 'update'));
+        
+        $grade_category->fullname = 'Updated info for this unittest grade_category';
+        $this->assertTrue($grade_category->update());
+        $fullname = get_field('grade_categories', 'fullname', 'id', $this->grade_categories[0]->id);
+        $this->assertEqual($grade_category->fullname, $fullname); 
     }
 
     function test_grade_category_delete() {
-
+        $grade_category = new grade_category($this->grade_categories[0]);
+        $this->assertTrue(method_exists($grade_category, 'delete'));
+        
+        $this->assertTrue($grade_category->delete());
+        $this->assertFalse(get_record('grade_categories', 'id', $grade_category->id)); 
     }
 
     function test_grade_category_fetch() {
+        $grade_category = new grade_category(); 
+        $this->assertTrue(method_exists($grade_category, 'fetch'));
 
+        $grade_category = grade_category::fetch('id', $this->grade_categories[0]->id);
+        $this->assertEqual($this->grade_categories[0]->id, $grade_category->id);
+        $this->assertEqual($this->grade_categories[0]->fullname, $grade_category->fullname); 
     } 
 
+    function test_grade_category_get_children() {
+        $category = new grade_category($this->grade_categories[0]);
+        $this->assertTrue(method_exists($category, 'get_children'));
+        
+        $this->assertEqual(3, count($category->get_children()));
+        $this->assertEqual(5, count($category->get_children(0))); 
+        
+        $category = new grade_category($this->grade_categories[1]);
+        $this->assertEqual(1, count($category->get_children())); 
+    }
+
 // GRADE_CALCULATION OBJECT
 
 // SCALE OBJECT