The Scouting Book For Boys (2010).
This underseen British gem from last year features many striking similarities to Deep End, so many that there's no way it couldn't have been an influence. That film, too, is about an immature boy falling in love with a much more experienced older girl who's taken - and the films share similar shockingly downbeat endings, and both raise similar ideas about the tragicness of young love, and the dark immaturity of jealousy. Both are masterpieces, and I highly suggest you check The Scouting Book For Boys out if you loved Deep End.
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