Problems with praying Jumuah at non-muslim school

I go to a non-muslim school with barely any muslim boys there, and the majority of them do not take their religion seriously. The school did not allow me to leave at lunch to pray at the mosque. I go to the school prayer room every Friday to pray Jumuah, however, I find myself to be alone there and that none of the other boys have showed up. Due to this, I resort to praying Dhuhr. Am I required to go around the school and find some boys every Friday and call them to pray with me? I tried this once with another boy, and he said he would come pray Jumuah with me next Friday, but he did not come. Am I sinful in this situation? I don't know what to do.