I reviewed your power distribution board. I think it needs more safety features before it can safely be entrusted to the hands of K-12 kids. Couple of comments:
- The battery input is unfused. I would HIGHLY recommend adding one.
- I know you guys wrote in Github about how people should not plug in voltages above 8.4V, and not overdischarge batteries, but I would not trust K-12 kids to follow those instructions :)
It would be best to add a overvoltage, overcurrent and reverse polarity protection circuits. Those are pretty simple and should not take much space on the board. Jerri Ellisworth has a great video where she explains these circuits in detail, and how to make them low-cost: https://www.youtube.com/watch?v=QZ0WXQWND-I
- I would add a schmitt trigger circuit to sense the battery voltage and feed that as a digital input to the Raspberry Pi. If the batteries are too low, the Pi then can throw an audible alarm and disable the servos. This would prevent kids from overdischarging their batteries.
As a future addition, I think it would be sweet to add a Teensy somewhere. Then students would be able to easily add extra sensors and have their robot respond to changes in the environment etc. So much potential for fun.
Congrats again!