It depends on the school's part time program. You need to meet a certain minimum credit requirement per semester. If that particular school's part time program meets that minimum credit requirement, then you're in. If it's not, you're out.
I can't remember the specifics, but if you look around a bit, you'll find it.
But you should know that you can't work more than 20 hours a week if you do make it into a PT program on an F1 visa, and that employment has to be on-campus. (This does not include OTP or CTP, but you should save those for summers, anyway.)