We allow 7th and 8th grades to join the team, but do not actively recruit them. In practice, this has only resulted in a couple joining - one is currently a senior, and joined back when her sister was a team captain and both her parents were mentors - it didn’t make much sense for her to stay home alone all build season! Another is currently in 7th grade. She saw the team many years ago at a demo and wanted to join ever since… she’s helped us once a year as a “consultant” to design and make the sponsor stickers on the robot (which her family donates) - she still does that now that she’s an official team member, and they look better than ever!
We’ve had a few others “try out” the team in the fall, but ultimately decide not to stick with it for build season. We essentially say that younger students join in the fall, which lets us see how they fit in with the team and then have a discussion with the parents about what’s best for the student - sticking with it or waiting until they’re older. It’s a combination of looking at maturity and comfort levels.
As far as the team, as a whole, goes, I haven’t seen any cons, only pros. Younger students tend to have more buy-in later in their career. They tend to do better, and move ahead of the curve of their peers (reaching leadership positions soon, contributing more, etc) on their successive years, which makes sense - it can be a great boost to the team’s confidence and abilities to have someone experienced sharing that experience! They also act as recruiters, making their graduating classes more heavily involved with robotics than other classes (We’re graduating one of our largest and most capable classes this year!).
For the individual students, however, there can be difficulties. They’re often working with much older students, which can be intimidating - you need to make a real effort to ensure the team is inclusive and supportive of all members, and make the younger members feel valued. They’re often shorter than the average student (but not always!), which can make using shop equipment difficult, or introduce difficulty with working table heights - and issue not necessarily limited to younger students, but something to keep in mind. There are limits in STIMS for registering with the team online - I believe the age limit is 13. We ran into that when we did our registration push last fall, and had to wait until the 7th grader had a birthday to get her registered.
The last issue really comes into play much later - 6 years on a team is a lot. For many students, by the time they’ve hit the end of their 4th year, they’re ready to move on. They’ve learned what they can, they’re inspired, and want a new challenge. 5 years doesn’t seem too bad, but that 6th year can be a bit of a burnout. They’ve seen it all, done it all. I think it’s important to get them to shift around and get involved with something new on the team so they have a new challenge that they aren’t already an expert at.
There is a hard upper limit (12th grade), but a soft lower limit - a recommendation of 9th grade, but you can go lower if you want. The decision, for us, came down to the Minnesota State High School League bylaws. As FRC is an officially sanctioned MSHSL sport, we go by their rules, which state sports and activities are eligible for 7-12 graders. Schools may make other limits, but we want to be as inclusive as possible, and it’s nice to have a hard floor provided for us.