Deleting Datagrid contents

<?xml version="1.0" encoding="utf-8"?>
<mx:WindowedApplication xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute">
<mx:DataGrid id="studentDetails" x="216" y="41" dataProvider="{listCollection}" itemClick="onItemClick(event)">
<mx:columns>
<mx:DataGridColumn headerText="Name" dataField="name"/>
<mx:DataGridColumn headerText="Age" dataField="age"/>
<mx:DataGridColumn headerText="Sex" dataField="sex"/>
</mx:columns>
</mx:DataGrid>
<mx:Button x="311" y="237" label="Delete Student" click="onClick(event)" id="deleteButton" enabled="false"/>
<mx:XML id="sampleXML" format="e4x" xmlns="">
<students>
<student>
<name>Michael</name>
<age>12</age>
<sex>Male</sex>
</student>
<student>
<name>Jesse</name>
<age>15</age>
<sex>Female</sex>
</student>
<student>
<name>Ben</name>
<age>10</age>
<sex>Male</sex>
</student>
</students>
</mx:XML>
<mx:XMLListCollection id="listCollection" source="{sampleXML.student}"/>
<mx:Script>
<![CDATA[
import mx.events.ListEvent;
import mx.controls.Alert;
public function onItemClick(e:ListEvent):void
{
deleteButtonEnableToggle(true);
}
public function onClick(e:Event):void
{
deleteButtonEnableToggle(false);
listCollection.removeItemAt(studentDetails.selectedIndex);
listCollection.refresh();
}
public function deleteButtonEnableToggle(val:Boolean):void
{
deleteButton.enabled=val;
}
]]>
</mx:Script>
</mx:WindowedApplication>