There are many teams which are comprised of students from
more than one high school . Each team has its own rules about who they will accept and who they won't - some teams will only accept students from high schools who do not already have a team.
A part of me thinks maybe you need to seek out ways you can better work with the team from your present high school. In the workplace you will not always have supervisors or co-workers that you get along with, but you have to learn how to work with them just the same.
If you feel you must join the other team, ask to meet with the team leaders to clarify their team's rule on this issue. You don't want to create any animosity with your new teammates. And then let your old team know that you are moving to the new team, and why. But do it in a manner that can help the old team improve. You don't want to be the cause of any bad feelings between the two teams.