Hey !
Changing of steam is not what I would suggest but if you feel that science is not your cup of tea then you should do what is the best for you. In arts you have English as one of your major subjects. If literature is what favors you then go for it. You have to write elaborated answers in board exams whereas in science you can get away but just stating facts. In science you would have a lot of things to mug up and remember whereas in arts you dont have that much of pressure. Whether you will do good in your boards after that totally depends on how you cope up with it and how well you are in that subject. Hope for the best. All the best.

Hi aspirant
Since you want to change your stream from science to arts in class 12th , it depends completely on you how well you cope up and study to score good.
In arts stream you have to write long answers and give facts and details in every question you attempt. And hence depends on you how well you present your answers  to score well.