so honestly it depends on what your plans after graduation are, and what your arrangement is.
A couple of points
1. If you plan on working with them after graduation - you need to be respectful and follow the proper protocols in place for time off or else risk getting that job after school. There is nothing wrong with taking the time off, and trust me, we all need it for family / mental health.
2. Do you have a set schedule (rotating weekends, etc)? If so, you can't just not show up - but you follow the process to get the time off. If you sort of just work prn - you can simply say you are unavailable for that time and offer to make it up later when other people need time off.
3. For example when I worked (at a place with all interns + one full time non-intern tech). We all had our set weekends, and we would trade accordingly. We would sit down at the beginning of each semester and work out the schedule based on our classes. When it came to holidays, we would do the same, sit down and work it out amongst us - is that an option for you?
4. I had two examples of people not following the "rules" and it definitely left a sour taste in my mouth as their manager, and definitely had the potential to affect their jobs down the road after graduation as I have a lot of contacts - I would never go seek out ways to mess with their careers, but if I was asked I would be honest.
a. Our interns have set weekends (every 4th) and if they can't work, it is up to them to find a replacement. One called me up 3 weeks in advance to tell me his flights were changed by the airline and now he wouldn't be back until 3 days later than originally planned . This is complete BS - I fly a lot and anybody with half a brain knows that doesn't happen. I did call him on it as I went online and saw open flights on the day before he was supposed to work on his airline. He basically just stammered - he then quit without giving notice. I was called from a friend about his residency application - I basically let her read between the lines without saying specifics.
b. Another person who had already given me their quit date a few months out had something planned for 6 months on her weekend- and never really even tried to get someone to cover. I told her our policy - she said "no one will work for me". Again - she didn't even really try (didn't offer a trade or anything as I saw her emails) - basically she then called out the day off - I let her know how unprofessional that was and how things like that can have unintended consequences down the road.
so the point being, just be professional about it - I know if you work for a big coporate chain, they don't care about you as a person, but depending on what happens after graduation you might need that big corporate chain to pay your bills.