Here's the info from the latest edition of my Universal guide:
"There are occasional Teen Nights ($12), alcohol-free dance parties for 13- to 19-year-olds, lasting from 8:00 p.m. to midnight. Parents get a Party Pass as part of the teens admission and teens get the first soft drink free. On these nights, the groove reverts to adult form at the witching hour. Teen Nights are more frequent during the summer months and are listed on the CityWalk Times & Info brochure."
Teen nights are not a regular once-a-week event, so you'll need to check the brochure or call 407-224-2691 or 407-224-3663 for more info.