Another thing that you are doing wrong is changing them and not letting them practice their religion/culture. As a school, you want to teach students things, Correct? But if you try to change the students and make them unhappy, they will not learn as well, if you discover what the students like, and use that as an advantage to their learning, they will learn much more efficiently.
You are also doing wrong by not letting them talk about the school to their parents, if you are scared that people will know about the ways of the school, then you are for sure doing something wrong and/or bad to the students. You also should know that if students want to run away, then your school should be treating students better, I’m sure that all of the teachers at the school have made a mistake and haven’t gotten punished, so then why would you punish the students? It only makes it worse.
The students hate you, is that really what you want? It only makes learning harder for the students.
So change the rules, make it more beneficial for the students and less abusive.