Students who have been in trouble in high school better have a heart-to-heart with their school counselor and take a look at their transcript before applying to colleges. Colleges are looking for good academic students and also students who are less likely to cause trouble on campus. One behavioral infraction in high school can be enough to keep a student out of college.
There is so much competition to gain admission to selective colleges that students who have a checkered behavioral history in high school have reason to be concerned about their admission chances. No college president wants to increase the chance of being on the front page of newspapers for negative reasons. There is no up-side for colleges to admit students likely to malfunction. The best predictor of an acting-out college student is what a student did in high school.
If you know a ninth grader, clue them in to this down side of breaking the rules. Students who have been in even minor behavioral trouble are often suspended in high school. College applications routinely ask students if they have ever been suspended for any reason (including in-school suspensions).