Re-applying for Visa as a student to travel abroad

I go to an international school and just turned 18. I had to go back to my home country to get a Chinese entry permit and was given an S2 single entry. I'm currently in China and need to travel with my school on a trip, however since I only have one entry left I will not be able to come back into China. I have multiple trips coming and I need to know how to deal with this situation without travelling back to my home country to re-apply for a entry permit.