Destroying Multiple Objects with Tags

I am trying to destroy a grid when a button is pressed. Each grid square is a child of one other one. This script is attached to the button.

#pragma strict

function OnMouseEnter () 
{
	renderer.material.color = Color.red;
}

function OnMouseExit ()
{
	renderer.material.color = Color.white;
}



function OnMouseUp ()
{
	var grid = GameObject.FindWithTag("Grid");
	
	renderer.enabled = false;
	
}

Try this instead

http://docs.unity3d.com/Documentation/ScriptReference/GameObject.FindGameObjectsWithTag.html

What you are using is only finding one object. The reference here tells you how to enumerate all the objects into an array. You can do what you want with them from there. The example should be in the reference of how to do this.