I used these kits with two classes, Year 4 and Year 5. The students thoroughly enjoyed making both the Balloon cars and the Solar cars. They were totally surprised at how quickly the solar enegry powered the cars. Two suggestions that I have would be: - Supply larger balloons for the balloon cars, as the students struggled to blow them up, and they did not have the capacity to propel the cars. - Make a note on the Solar car instructions that the gear that is attached to the rear drive shaft needs to be installed on the right-hand side (otherwise the car drives backwards)