I'm in CMI (Chennai Mathematical Institute). Believe me, it is one of the BEST Colleges in India to pursue Mathematics (Along with Computer Science or Physics whichever you want). I would say there are merely 3 or 4 institutes in India which ca compete with CMI.

So, I would say CMI is one of the best Institutes in India to pursue B.Sc in Mathematics (Along with Computer Science or Physics).

Thanks and Regards

A CMI-ite