I think:

1, this problem is a "contractual relationship". The premise of the contractual relationship is that both parties voluntarily send their children to private schools to form such a contractual relationship. As long as the agreement in this contract does not violate the prohibitive provisions of the law, it shall be deemed as legal and valid.

2. Looking back at the laws of our country, the so-called "compulsory education is completely free" is put forward for public schools, which is intended to restrict the relationship between the subject of public education and citizens, rather than the relationship between the subject of private private education and the counterpart of the contract. Therefore, sending children to private schools should be adjusted by applying contract law.

Students in private schools have not given up the right to receive compulsory education. Once they drop out of private schools or transfer to public schools, they still enjoy the policy of compulsory education.