Hi Arnold Roy,

You have studied commerce in 10th ICSE then you cannot opt for taking science in 11th and 12th because you don't have basic knowledge of sciece. Though it is very difficult you will be not allowed to take science.

However if u really want to switch you can opt for IB(INTERNATIONAL BACCALAUREATE) instead of 11th and 12th and do science subjects as major in it.

Or else you can even opt for business mathematics that will help you to treat commerce at par with science.

ALL THE BEST.

Yes you can change your stream from commerce to science after 10th. But can't change it in 11th.