Shirk,kufr matter of aqeedah in the field of islamic matters

1) I study in Hindu school and there are kufr prayers in that school in the morning assembly i remained in their but i didn't take part in those prayers nor clasped the hands like theirs and u hated in my heart . Is this Shirk/kufr ? There is no Islamic school near me and my parents are forcing me to go to this school and i have not any option but to go to this school. And i also cannot left the school because I am in 10th if i left the school i have to study the whole two years starting from 9th and might be my father didn't get my admission done into another school. 2) I did not do that kufr prayers nor clasped hands like theirs but my teacher is now scolding me then i have said her that i have so much pain in my hands and in reality also I had so much pain in my hand.so my teacher said that give me a letter stating the problem and with the medical certificate (although i have) and to state that when I have been praying kufr prayers.I have almost 4 months left in this school. So is it right for me to send her application with medical certificate until i pass the school.Is there any harm upon me in future?