You can consider below names as these colleges are decent to pursue B.Sc Maths course -

St. Stephen’s College

Loyola College

Department of Science (Christ University)

Miranda House

Hansraj College

Fergusson College

Madras Christian College (MCC)

Hindu College

Sri Venkateswara College

Ramjas College

Stella Maris College - Chennai

St. Joseph's College - Bangalore etc

Good Luck!!!