What is the legal notice period a teacher has to give to the management before quitting?

A particular pre-school in Hyderabad has a policy that teachers have to give a notice period of 3 months before quitting. But as the management forces the staff to deposit their education certificates with them it is at the managements mercy that the staff gets to leave the organization. It could be even one to two months after the last date specified by the staff member. Is this fair and is this legal?What is the legal notice period a teacher has to give to the management before quitting?
In Texas, a teacher has a written contract with the school district. The notice required is stated in the contract. This is usually 45 days before the first day of the new school year. A teacher resigning during the school year is breaking the contract. The school may release them from their contract. If a school chooses not to release the teacher, the school can petition the State Board of Educator Certification to suspend the teacher's certification for a year. Most teachers work under a contract which they and the district has signed. This contract outlines when and how a teacher may resign without penalty.What is the legal notice period a teacher has to give to the management before quitting?
As in similar question I have explained all what these people are doing is illegal. Normally 1/2 months are sufficient for notice but as per agreement one has to follow, but to take possession of certificate is illegal.