AppleScript: Quit All Applications

I often use this script with ARD to quit all open apps.  Useful for when some malevolent students sets every app to open at login.

tell application "System Events" to set the visible of every process to true
set white_list to {"Finder"}
	tell application "Finder"
		set process_list to the name of every process whose visible is true
	end tell
	repeat with i from 1 to (number of items in process_list)
		set this_process to item i of the process_list
		if this_process is not in white_list then
			tell application this_process
			end tell
		end if
	end repeat
on error
	tell the current application to display dialog "An error has occurred!" & return & "This script will now quit" buttons {"Quit"} default button 1 with icon 0
end try