If I'm in the US on a student visa but not enrolled in a school, can I apply to another school using the same visa?

If you have fallen out of status, then you must ask the correct department for reinstatement or seek some other means to reacquire your F1 student visa status. There are limited reasons to get reinstatement, so many are denied. As a result, I strongly recommend an appointment with a competent and experienced immigration attorney before there are any more complications. The above is general information, not legal advice, and does not create an attorney client relationship.