Can u be forced to retain 9th grade?

High school is different from middle school. In NY middle school if you fail more than two classes and don’t do summer school (or fail the classes in summer school) you get held back and repeat the whole grade, retaking all of that grade’s courses. Parents can also voluntarily withhold you as well. School shrinks can recommend / request parents to withhold the student but cannot do so themselves.

So yes you can