The film is not for everyone. Some might think the acting is bad when it is actually understated and natural. There are no obviously evil acts and there are no stunningly beautiful moments. There is a lot of indecision, an lot of conflicting feelings.
Actually this film takes a very honest look at a very complex subject, Sex with minors. It is complex because the characters are trying to deal with love and sex when her body and hormones are still developing and both of their minds and personalities are still developing. Complex also because society has very simplistic views of sex with minors, and complex, because the characters don't know if society is right or if their instincts are right.
Some will not like the movie because it leaves unanswered questions. Questions such as who was really in charge of the relationship, who was damaged, did good come out of it, was it art, who was damaged more, did some of the problems with their relationship stem from it being forbidden by society, did some of the problems stem from their own immaturity, and probably most important, was this truly a crime?
The film is resolutely neutral on all of this, and it is this neutrality that is its strength. It is the reason for the understated acting, the simple sets, the lack of background music, soft lighting, and the general "flat" presentation. The message is clear. We don't really understand this kind of relationship today, and quick judgments are bound to be shallow.