Hi there,

Studnets can change there streams from commerce to science or science to commerce while studying in class 11th . After completing class 11th Studnets can not change their stream . If Studnet want to take science stream then he/she will have to do class 11th again.

Other option that Studnets have is that they can change their board like they can shift from cbse board to state board. But I would advise you to not do such change as science stream requires strong background of class 11th .

Furthermore,  one can make variation in courses during college .

Hope it helps you

Good luck!