similar movies

I would recommend to you The Boys of St. Vincent.

It was made two years before Sleepers, and deals with very much the same topic. It's a three-hour made-for-TV Canadian movie that takes place in two parts: the first part deals with the abuse several young boys suffer under the hands of the priests at a Catholic school; the second part takes place 15 years later and shows the long-term effect the abuse has had on the boys, as well as their attempts to bring the priests to justice.

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count of monte cristo
primal fear
ghajini (bollywood film)
shawshank redemption
i spit on your grave

Celebrity (1984) (TV mini-series)
State of Grace (1990)
Bound by Honor (aka "Blood In Blood Out") (1993)
The Lesser Evil (1998)

Also, Agatha Christie's long-running stage play "The Mousetrap" is about revenge for child abuse that happened long ago.

Look at "The Magdalene Sisters" (2002). It has a similar story to this one, except the protagonists are female. Another one is "King of Devil's Island" (2010).

These movies don't center on revenge, but they're very similar in their portrayals of abuse in juvenile detentions.