What happens to a High School student if they reach age 19 (or whatever the maximum age) before graduation, due to being held back a year or so?

I’m not sure they even hold students back anymore. I haven’t heard of even a school-age kid being held back since the early 1990s,

In my county, maybe my state, you cannot be in regular high school past age 18. This might not apply to students who are continually enrolled. The student must go to an adult education program.

But if someone has been held back a year or more, they could quite easily exceed age 18.

This has not happened to anyone I know, so its only hypothetical. But I have recently learned that once a student is older than 18, that is, 19 or older, they have to enroll as an adult in an adult education program

And I HAVE known middle school students in the past who would eventually reach that dilemma due to being held back.

Of course, in some cases, it is a liability to have young adults among high school students. This is why the rule was instated.