1. You say you are "setting it up on your student's computers". Do you mean these are school computers, and the students will share them? Or that these are the student's own computers?
2. What are you setting up? Free 7 day trials, individual accounts, enterprise/school license?
3. If it's an enterprise/school license, are you adding a paid license for each of the students, as account adminstrator?
4. You say "they keep ending up with trial versions". There is no separate trial version. You get a trial if the user signed in does not have a valid subscription. Have you checked the account status on those computers?
5. Sometimes malware on a computer can stop Adobe subscription checking. Are these computers that students could previously install software on?