Hostel rent taxable or exempt

Yes. Hostel rent is liable to GST. Because the exemption granted to Charitable institutions registered under section 12AA of Income tax act are for the limited purposes of services by way of charitable activities and it doesn't cover renting of premises except for limited exemption provided for religious precincts.

The charitable institute or trust services are exempted only in case of renting of precincts of religious places & where the room rent per day is not more then 1000/- . (Ref : Notification 12/2017 CT rate , s.no 13)

So you do not cover under the same hence its taxable .
upto 7500/- it's 18% GST and above 7500/- it's 28%

its mean we have to keep record of hostel rent Right?