selected as student excange program

Dear, I don’t think it will cause any problem.
If you hold an X1 type, you can get a residence permit after you entry. And you can use the residence permit to exit and re-enter for many times.
If you hold X2 type, after you exit on third month, you need to re-apply for a new X2 type when you want to reenter to finish your study because the X2 type just has single entry.
But no matter which type you hold, you can still enter PRC and continue your study.