Hey Anuja,
TISS has really gained a good reputation among the people since quite few years. It holds an exam called TISSNET, where people applying for MA and MBA have to give this exam and score the minimum percentage, as mentioned in the criteria.
There is no particular site as such, where you can prepare it fully, but I am listing below few steps to take the memory based TISSNET papers and mocks :-
Hope this helps. Happy solving !
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