Thank you for sharing your concern. The age breakdowns of the different types of Students will be clarified further in the August Game Manual update.
EDIT: In the August 16th Game Manual update, the definition of Student was updated as follows:
Anyone born after May 1, 2004 (i.e. who will be 15 or younger at VEX Worlds 2020). Eligibility may also be granted based on a disability that has delayed education by at least one year. Students are the individuals who design, build, repair, and program the Robot with minimal adult assistance.
• Elementary School Student - Any Student born after May 1, 2007 (i.e. who will be 12 or younger at VEX Worlds 2020). Elementary School Students may “play up” and compete as a Middle School Student.
• Middle School Student - Any eligible Student that is not an Elementary School Student.