When I first time successfully explained Newton's laws to a 4-year-old, I stop believing in that "kids are not ready" crap. The point is to make it fun and to adjust your methods, they have no problem with understanding the knowledge as long as you explain it to be interesting to them. I am glad that you are doing such an awesome job with your kids and as for the teachers in schools, yeah, we have the same problem here. They experience a burn-out after some time and become completely uninterested. Not all of them, of course, but unfortunately the vast majority of them. The problem is their paychecks are too low and the joy is becoming harder with each day so I do not blame them, on the contrary. I feel sorry for them and am grateful for all that they are doing.