Per diem question

I am looking at a per diem CNA position at a local hospital and I have some questions about y'alls experience with per diem work...

Do hospitals usually look for on-call anytime-anywhere per diem workers or have you found that they are willing to work with someone who can only cover 3-4 days a week?

I will be in school a few days a week in the spring - I'd like to be sure that there would be no conflict. I am only used to working in SNF/LTC so I have little to no experience with how hospitals manage this.

Thanks!