I am in the Plano ISD and most of the team sports have tryouts which have been concluded by now. The team sports are also run under the UIL rule. UIL has specifics on team members regarding grades, qualifications, etc.
Team sports in Plano and Arlington as well (all over TX) are very compeitive and most of the students on the teams have been there for some time. We have some Freshmen (9th grade - high school) playing a variety of sports at the Varsity (12th grade -- Sr High School) level.
If your child has never been in team sports or shown interest, I would think this is not the time to start. However, if you have a very driven child who is willing to work extra hard to pull it off, good luck.. it can be done.
My daughter is Varsity Cheer and has been cheering since 8th grade and she never had to take PE as long as she was active on the cheer squad. My understanding is that the marching band and the drill team are not in PE either due to all the working out and training that takes place outside the classroom.
Team sports take up a LOT of time outside the classroom which involves a good amount of $$ per sport, fundraising for the sport, and a lot of family volunteer hours to make things happen.
Good luck