I have known many High School coaches through the years, both elite and/or just your average high school coach. I can honestly say, I haven't known one that I ever got the impression would not give an honest assessment to a college program asking about one of their players. Especially if the young man has committed to that school.
High School Coaches should do everything in their power to help get these young men into a college football program. Everything but lie or withholding information about attitude. Tell it like it is and let the school recruiting the young man decide for themselves whether or not he is a take.
Most HS coaches will do the right things although I have known some who would not send film to a particular college if they held a grudge or had a total dislike for the school. I have heard statements made to the effect that Coach ------- can go t0 ___ if they think I will send a player to them.