Actually had a idea for something like this, but the protagonist was the 6 year old, and was freed after 10 years. Then she was recruited by a agency to find the people that murdered her parents and framed her.
"Legally Blonde" - certainly in my top ten list of my favorite movies of all time (even beating "Judgment at Nuremberg"!). It has served as an academic inspirational tale for me for the last, longer than I care to admit, number of years... ;-).
Technically, all students involved who submitted their own names were 17 or older--the Wizarding Age of Majority. Basically, in the eyes of the government, they were adults and therefore did not need parental permission.