Why do we teach lies at school?

I learned something interesting recently about gravity. Well, it's something I'd heard before plenty of times but, a bit like how it took reading The Selfish Gene to really understand evolution, it wasn't until I read Why does E=mc2? by Brian Cox and Jeff Forshaw that I got a glimpse (it's more difficult to understand than natural selection) of what it means when people talk about gravity and 'curved spacetime'.

This post isn't about the subject matter of the book, as such, rather what it got me thinking about some of the things that are taught to children in school (I'm currently training to be a primary school teacher, so this is a significant question for me). But I should explain the basic principle so you know where I'm coming from.

One of the last chapters in the book describes gravity as something we observe which hints that spacetime is curved. To do my best to explain briefly, let's first think about forces. There is a law that we're all probably familiar with that objects will remain at a constant velocity (either sitting still or coasting along) unless a force acts on them. To persuade yourself of this, just think how obvious it is that an object won't spontaneously start moving without a force. Then you only need to realise there's no difference to Nature between sitting still and moving without accelerating. So it turns out that the deeper rule is that an object moving at constant velocity won't spontaneously accelerate (imagine a world without friction, there'd be no way to stop unless you hit something!).

So, to gravity. Gravity is taught as a force because objects tend to fall and it looks as if they're being pulled away from what would have been their natural course, just as if a force were acting on them. Certainly a constant downward force would have the same effect on an object in space. But in the book it is revealed that our best understanding of physics describes the natural course of objects to be along straight lines through spacetime, spacetime which is curved by the presence of mass. So an object you're holding in your hand would coast along a straight line through space time that would bring it closer to the Earth, if you let it go. You're constantly bumping against its spacetime-momentum, like you would bump against someone if you tried to walk in a straight line parallel to each other due to the curvature of the Earth's surface. It's not that you're attracted to each other, it's that your paths intersect.

In other words, gravity isn't a force. This is crucial, because it is explicitly described as a force in primary science. Watch this (brilliant) video I found of Dr Richard de Grijs teaching primary school children about gravity. I'm sure he's heard of Einstein, so why is he teaching children that gravity is a force? Perhaps, I've been thinking, he shouldn't be...

I am still finding a lot of the concepts (pretty much anything to do with movement through spacetime from multiple perspectives) in Why does E=mc2? to be very hard to focus on and I strongly suspect this is because it contradicts what is drilled into our heads in school. What sort of obstacles are we putting up with miseducation like this?

We don't have to teach children advanced physics, obviously, but should we teach them lies? Why do we still teach children that gravity is a force, if we know it's not? Is it really necessary? Surely it would, if nothing else, be better to just avoid discussing it, as we avoid discussing the relationship between magnetism and electricity, if there's really no way of describing it to them. Then when they're older they won't find it such a hurdle to wrap their head around the actual theories we use to understand Nature.

And perhaps it is possible to teach children the rudiments of these things. Isn't the point of the curriculum to work out the best way to break down complicated subjects into steps that children can handle? Is it really more complicated than other scientific concepts, or is it a very new way of understanding Nature?