diff --git a/grade/edit/tree/index.php b/grade/edit/tree/index.php
index 26fb0bb..bb86c1d 100644
--- a/grade/edit/tree/index.php
+++ b/grade/edit/tree/index.php
@@ -89,12 +89,35 @@ if (has_capability('moodle/grade:manage', $context)) {
 // Change category aggregation if requested
 if (!is_null($category) && !is_null($aggregationtype) && confirm_sesskey()) {
     if (!$grade_category = grade_category::fetch(array('id'=>$category, 'courseid'=>$courseid))) {
         error('Incorrect category id!');
     }
     $data->aggregation = $aggregationtype;
+    
+    // RT# 57186 20100115 kimx0794.
+    // Go through and set the aggregationcoef for all the children to 0 when switching from WM to SUM/SWM.
+    if ($grade_category->aggregation == GRADE_AGGREGATE_WEIGHTED_MEAN AND ($aggregationtype == GRADE_AGGREGATE_WEIGHTED_MEAN2
+        OR $aggregationtype == GRADE_AGGREGATE_SUM)) {
+    	$grade_category->children = $grade_category->get_children();
+    	foreach ( $grade_category->children as $useditem) {
+    		$useditem['object']->grade_item = $useditem['object']->get_grade_item();
+    		$useditem['object']->grade_item->aggregationcoef = 0;
+    		$useditem['object']->grade_item->update();
+    	}
+    // Go through and set the aggregationcoef for all the children to 1 when switching from SUM/SWM to WM.
+    } elseif (($grade_category->aggregation == GRADE_AGGREGATE_WEIGHTED_MEAN2 OR $grade_category->aggregation == GRADE_AGGREGATE_SUM)
+              AND $aggregationtype == GRADE_AGGREGATE_WEIGHTED_MEAN) {
+        $grade_category->children = $grade_category->get_children();
+        foreach ( $grade_category->children as $useditem) {
+                $useditem['object']->grade_item = $useditem['object']->get_grade_item();
+                $useditem['object']->grade_item->aggregationcoef = 1;
+                $useditem['object']->grade_item->update();
+        }
+    }
+
+
     grade_category::set_properties($grade_category, $data);
     $grade_category->update();
     grade_regrade_final_grades($courseid);
 }
 
 //first make sure we have proper final grades - we need it for locking changes
diff --git a/lib/grade/grade_item.php b/lib/grade/grade_item.php
index d4199d6..8a5f175 100644
--- a/lib/grade/grade_item.php
+++ b/lib/grade/grade_item.php
@@ -1208,14 +1208,22 @@ class grade_item extends grade_object {
             return false;
         }
 
         // MDL-19407 If moving from a non-SWM category to a SWM category, convert aggregationcoef to 0
         $currentparent = $this->load_parent_category();
 
-        if ($currentparent->aggregation != GRADE_AGGREGATE_WEIGHTED_MEAN2 && $parent_category->aggregation == GRADE_AGGREGATE_WEIGHTED_MEAN2) {
-            $this->aggregationcoef = 0;
+        // RT# 57186 20100115 kimx0794.
+        // If moving from a non-SWM/non-SUM category to a SUM/SWM category, convert aggregationcoef to 0.
+        if ($currentparent->aggregation != GRADE_AGGREGATE_WEIGHTED_MEAN2 && $currentparent->aggregation != GRADE_AGGREGATE_SUM
+            && ($parent_category->aggregation == GRADE_AGGREGATE_WEIGHTED_MEAN2 || $parent_category->aggregation == GRADE_AGGREGATE_SUM)) { 
+            $this->aggregationcoef = 0; 
+
+        // If moving from a non-WM category to a WM category, convert aggregationcoef to 1.
+        } elseif (($currentparent->aggregation == GRADE_AGGREGATE_WEIGHTED_MEAN2 || $currentparent->aggregation == GRADE_AGGREGATE_SUM)
+            && $parent_category->aggregation == GRADE_AGGREGATE_WEIGHTED_MEAN) {
+            $this->aggregationcoef = 1;
         }
 
         $this->force_regrading();
 
         // set new parent
         $this->categoryid = $parent_category->id;