Chinuch as tochacha for teenagers & young adults

 The mitzva of chinuch is generally understood to be from about 5 years till bar mitzva. However there is another aspect of chinuch which is giving tochacha. Both are learned from the same verse in Mishlei (22:6).

Kiddushin(30a) says, Raba said to R. Nathan b. Ammi: Whilst your hand is yet upon your son's neck,[you should get him married] which is  between sixteen and twenty-two. Others state, Between eighteen and twenty-four. This is disputed by Tannaim. Mishlei (22:6) Train up a youth in the way he should go: R. Judah and R. Nehemiah [differ thereon]. One maintains, [Youth means] between sixteen and twenty-two; the other affirms, Between eighteen and twenty-four.

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Rashi explains, When your hand is still on your son's neck - means when you still have power and influence over your son before he gets older and doesn't listen to your admonition you should get him married. ... Another explanation is that the time while you still have influence over him take care to teach him instructions & chastise him and this time is from the age of 16 until 22. Prior to this time he doesn't have the mental ability to accept your instructions & chastisements so much. On the other hand if you try chastising  him and pressuring him with punishments after the age of 22 there is concern that he might rebel - and this main understanding of this gemora. According to his way - meaning you should teach him in his youth the path that he should follow for the rest of his life. The time for this teaching is a dispute as to whether it is between 16-22 or 18-24.

Meiri (Kiddushin 30a), A person should always focus his attention of supervising his children and to continually give instruction and correction whether they are old or young. Nevertheless the proper time to make successfully reprimand him is from the time the mind starts maturing until it is mature. That is from the age of 16 to 24. Prior to 16 he doesn't have have sufficient maturity and after 24 he doesn't really listen anymore. So this is the best time to continually convey reprimands and instructions  regarding the son.: