Easy parenting with OSX
On the errant child's computer in the crontab of a logged in account:
* 23,0,1,2,3,4,5 * * * /usr/bin/osascript -e 'tell application "Finder" to sleep'
(It tells the computer to put itself to sleep every minute of every hour between 11pm and 5am.. of course if the computer is already asleep it doesn't do anything)