I didn't earn my internship in Changzhou American International School easily

I didn't earn my internship in Changzhou American International School easily. It wouldn't be possible if I wasn't fortunate enough to spot that school accidentally in the first place, or later failed to persuade my own teacher to allow my regular absence during every afternoon's individual study sessions. I was the teaching assistant of all math classes from Grade One to Grade Nine (the school had 120 students altogether). My major task was to help my math teacher scoring students' assignments and lead group discussions in his classes. I also offered tutorship for students who have problems with math after class. Working 1.5 hours every day for no pay in one's senior year when academic competition was fierce might not make sense to some people, but for me, getting involved in an international community and exploring in a brand-new world made all my effort worthwhile.

It looks good I think :)

Only one thing I would like to change:

for no pay -> for free

Thanx Yooyoung!You're absolutely right!