MAC address randomization should only affect those using captive portals, or some form of device based radius.
Couple things could be going on here. One, you have a time filter applied to this profile and the times are off. Two, the wifi payload is not correctly configured i.e. if your network is using a wpa2 password and you selected Automatic, WPA3 or WPA / WPA2 instead of just WPA 2 in the profile. One thing other thing to be aware of is that its possible students are tapping on reset network settings which I've seen zero out the password and since the profile is still installed and hasn't changed, it won't reapply.
Perhaps it's best to have someone trustworthy like yourself or a colleague to take a student configured iPad home, connect it to their wifi network and return the next day and see what occurs. If nothing does once or twice in a row then you have some or a lot of students with an "idle hands" problem.
