Hello,

If you're a student of 10th then your 10th board exams will be considered your Matric or Matriculation. There is no concept of changes is involved in this. If you want to change your board then you can fill up the form of some State Board, if dates are not passed for this year.

Now if you're an average Student and not good at Mathematics then I suggest you to take Commerce Stream. Commerce stream is the best for you as, Arts is very boring and Science is very very hard for an average Student like You. But if you are willing to become an Engineer or a Doctor then you Will have to pursue Science with PCM or PCB depends on the stream.

Good Luck.