Teams in VEX are not based on “grade level” but rather by date of birth. There is no “grade-level” definition for teams, and younger students can be on the same team as older students. The team will be classified as a MS or HS team based on the age(s) of the oldest students on the team.
For more information, please take a look at the definitions of “student” and “team” in the game manual: Links are here: