hello aspirant,

I hope that you are doing absolutely great.

With reference to your above mentioned query, i would like to tell you that if you are from art stream and want to change your stream to science in class 12th, then you can do so by writing the letter to your school Principle.

You might start with requesting your principal and submit a letter addressed by your parents regarding the issue. If you qualify for the subject as per the eligibility criteria,you might get the choice of your stream as well.

I hope that this will help.

best of luck for future.