Gratuity for teachers

1. Since Teachers were made part of the GRATUITY act from 1997 from when should we calculate gratuity of a teacher who joined in 1990. Should it be from 1990 or 1997.
2. A person who after working for 10 odd years left her job for 3 months now she is claiming Gratuity what is the rule.
3. A person works in one school for 5 years continuously and then leaves she then comes to my school and works for 6 years is she eligible for gratuity.

please let me know 

1 from 1990

2.asked resignation from her, then make payment. since she has worked more than 5 years, she is entitled for gratuity.

3. yes, 

Thankyou Mr. Kar. Just a clarification

#3 A teacher works for 7 years in school 1 gets gratuity then goes to school 2 works for 8 years gets gratuity then comes to my school and works for 6 years she still gets gratuity. This will make teachers make it a business to jump schools. Is there any way that we can circumvent this.

#2 This person left the job after 8-9 years and after 3 - 4 months rejoined what is her recourse.

The openion given by Shri Tripathiji is correct.As regards clarification sought by you.

1. Since the teacher has put up service in each school rendering him entitled to receive gratuity from each school,he shall be entitled to receive the same. Jumping the schools would not be more advantageous because in total he shall receive gratuity for 21 years. Even if he worked in one school for same period, his entitlement would be same.

2 If she has left employment after 8-9 years and joins again afresh she would receive gratuity for 8-9 years and has to again render five years contineous service to qualify for gratuity. If that 3-4 months gap does not interrupt her service, she would not be entitled for any gratuity,unless her service comes to an end.