Can I miss school for this , and is so can you help me come up with something to say to school.?

If you do not have a chemistry test, then you can skip school just this once.

If you have a test, then you should not miss school that day, because it will influence your grades.

Talk to your supervisor, and ask him if you could miss that surgery and attend another one in future, because you have a test at school.

You can try talk to your chemistry teacher, and see if you could take the test later.

You have to decide what's more important to you. If you decide to miss school for that, make sure to give your school a legit reason for why you were absent (yes, you will probably have to lie and say that you were sick or went on a college visit or something) and if you have a test that day, your teacher will probably let you make it up whenever you come back to school

I don't know, but school stinks and most of them have School Nazi Gestapo officers to come around and badger you/capture you.

Get a note from the person that's doing surgery and bring it to school the next day. It's an excuse if it has to do something with your career.