My son has been detained in class 8 by PRIVATE school

M y son is studying in a private school in delhi. He has been detained in class 8 by the school this year. As per my understanding of the right to education act this is against the law. On discussing this with the school authorities they replied that this private schools do not come under this act. and they can detain my child. Kindly clarify this for me. Also, please note that my child has scored more than 33% marks but the school says that the passing marks are 40%.

Praveen Soni