You have not posted the school is ;Pvt,Govt,aided,local bodies etc etc.
In any case:
Refer to payment of Gratuity Act,1972;
The employer is under obligation to supply the 'Notice of Determination of Gratuity' and payment within 30 days from LWD or interest @10%pa is to be paid.
You may write to employer ( under proper acknowledgment) that both have not been supplied to you and FormI is attached.
The leave encashment etc is as per enactments that apply to establishment say; Shops & Estbs Act and if you are covered by the de. of 'Employee' as in the Act you can refer to the enactments....................
If establishemnt and you are covered then establsihment can provide superior benafits, but not inferior.
Relate with Leave Rules and service rules for everything you want and write to employer, of course under proper acknowledgment.
Come back in case of any more issues.