My mouth almost hit the floor that no one said this! At least you did. I learned vectors in the 6th grade (without the numbers of course). I knew how gravity worked and how ships flew. Gravity sling shot was a piece of cake. Then later when they introduced the math of 4 wheels on the ground with friction and stuff it was just SO easy because I had known about that stuff for years. Also with the older kids you can start talking about how a circle is graphed with sin and cos inputs being the degrees of the circle and the output being the x and y of a unit circle. Then it is very easy to start understanding how adding these sin and cos and multiplying by the speed gives you the final vector. Once they get that show them how much better it is to do it with a 4x4 matrice.