I decided to travel to Europe for the time being. According to the information, you need to see the certificate, but the school is on holiday and you can't open it.

First of all, it depends on where you study and whether you are accompanied by your parents when you go out. As for the proof of studying, it can generally be supplemented by student ID card, admission notice and report card. In addition, you can write a copy of your school and explain why you can't issue a certificate of study. Specifically, I suggest you consult the travel agency that wants to join the group.