You might want to consider a way to bind transmitters on the fly. Consider buying some Servo cables and attaching them to a latching push button switch. That way, you don't need direct access to the receiver to plug in the jumper (and you won't have to worry about losing said jumper).

https://www.amazon.com/gp/aw/d/B0711V3BWN/ref=sspa_mw_detail_3?ie=UTF8&psc=1

As far as tires go, dollar flip flops and a hole saw kit will give you tons of versatility. (Letting students balance speed and torque is a great way to learn about power trade offs)

Edit 1: Oh! Remember to only use one red wire to power the receiver. Remove (tape back) the center wire on the second ESC. (Which are 10a, btw. Still fine with the N20, but 30a is the burst current)

Edit 2: These ESCs look like the same ones I use, and should be able to handle 3s, fwiw. Being able to power a 9v toy at 3s for cheap makes a huge difference.

Edit 3: Battery monitors can be useful too. You don't want students running down lipo batteries until they stop. Also might be good to pick up some lipo bags to use during charging.

https://www.amazon.com/WMYCONGCONG-Battery-Monitor-Voltage-Indicator/dp/B07RZJSZ1H/