Hi,

To change your stream, it is advised for you to contact your school mentioning why you want to make the switch. Quite a lot of schools have this option where you can change your stream after class 11th, but it depends entirely on the school administration.

For most of the technology related courses and major courses like B.tech, you will have to appear for entrance examinations which are based on both class 11th and 12th syllabus. So, it is entirely up to you to take the decision to change your stream at this point of time as you will have to work hard to catch up with other students who have already studied science in Class 11th.

I hope this helped you.