Assuming that Payment of Gratuity Act is applicable to such establishment in which you are working
GO thru:
Payment of Gratuity Act, 1972;1,2A
https://clc.gov.in/clc/sites/default/files/PaymentofGratuityAct.pdf
and check if your establishment is covered and you are eligible..
You may also go thru simple to understand: THE PAYMENT OF GRATUITY (CENTRAL) RULES,
1972 https://labour.gov.in/sites/default/files/ThePaymentofGratuityRules.pdf
and simple to understand Rules by your state
e.g; The Payment of Gratuity (Maharashtra) Rules, 1972
https://www.esipf.com/labour-law/the%20gratuity%20act.pdf
If you are a teacher and Act applies to establishment , you should be eligible;
GO thru details at; Discussion > Labour & Service Law > Gratuity > Is the private school teachers
applicable for gratuity ?
https://www.lawyersclubindia.com/forum/Is-the-private-school-teachers-applicable-for-gratuity--92288.asp