Dear Student,
For doing Bsc. In any specialization one has to first complete his 12th which I hope you have completed. For doing it you should clear the minimum eligibility criteria of 50% in your 12th. The cutoffs for bsc for most of the colleges don't go much high due to comparatively lesser demand. Following are some top colleges of India for Bsc. where you can apply :-

• St. Stephen's College, New Delhi.
• Presidency College, Kolkata.
• Lady Brabourne College.
• Banaras Hindu University.
• Jamia Millia Islamia.
• St. Xavier's College, Kolkata.
• Jadavpur University.
• Jamia Hamdard University.

Hope this might help you.

St. Xavier's College, Mumbai.
Christ College, Bangalore.
Ramjas College, Delhi.Madras
Christian College, Chennai.
Miranda House, Delhi.
Hansraj College, Delhi.
Fergusson College, Pune.
Hindu College, Delhi

These are some top ranking colleges.
You may also sort it by the stream of BSC you want to choose.