Nazir 29b - Chinuch until When?

The gemara tries to make the machlokes whether the father can impose nezirus on his son until he reaches o'nas nedarim or until he reaches gadlus, dependent on the machlokes whether it is based on a halacha l'moshe misinai (father is in control to impose nezirus until gadlus) or based on chinuch (father looses control at the age of o'nas nedarim). The rationale is explained by the gemara "since the child leaves the fathers jurisdiction (for nedarim), he no longer has an obligation of chinuch. Tosafos indicates, and the Rosh writes explicitly that there is no mitzvah on the father to be mechanech a child in a mitzvah that the child himself is fully obligated in -

דכל מצוה שהוא מחוייב בה אין אביו מחוייב לחנכו בה

Although the gemara falls off this teliya, the gemara never seems to reject this sevara. Therefore, it should follow that there is no mitzvah of chinuch on a father to be mechanech his son once his son reaches the age of bar mitzvah. However, in kiddushin 30a the gemara says clearly on the pasuk of חנוך לנער על פי דרכו that it means to train a child between the ages of 16 and 22 because that is the age of "na'ar" that the pasuk refers to and as rashi explains the chinuch at that stage will teach him a derech with which to live his whole life. From this gemara it seems the mitzvah of chinuch not only extends past bar mitzvah, but the ideal state to give mussar and be mechanech the child is after bar mitzvah.

v'tzarich bi'ur.