@DY I feel that our disagreement here is rather nuanced as i would agree that kids don’t really go off because of the frumkeit per se but rather because of the way it is represented to them or because of the way they are labeled if they do specific things. What people have to understand is that sometimes it is ok (depending on where they are at in life) for kids to be less frum than their parents and that it is not the end of the world. In fact for certain kids to be forced into levels of frumkeit they are not ready for can be very damaging. What I meant by absolutism is not just the people who are heavily machmir but even people who are just following the letter of the law can fall into this trap. I am referring to absolutism in ideology – where a kid could come out thinking that if he isn’t cut out for learning and feels like skipping class and playing basketball he might as well go and be mechalel shabbos since its all the same. Surprisingly enough this happens very often. I hope this clarifies things.
As far as the letter goes I feel that it is typically better to try to work with the parents to craft solutions as opposed to mandating a certain code of conduct through letters. Yes, some parents are really uninformed but a vast majority of parents whose kids do these things are aware of the situation and dont think its so bad because “teenagers will be teenagers.” In fact I have seen a case ironically where it was that kind of attitude that caused a kid to go otd. It does work both ways.