Every meal time, he is put in his highchair, strapped in, and 30 seconds later is standing on the table, beaming. We stopped strapping him in for a while, and he started eating better, but normally is standing up in his chair within seconds of being put in it. The same thing happens if he climbs into the chair himself - seated for seconds, then bounds to his feet, beaming. He has fallen from the seat more than once, when we haven't quite been quick enough to get to him.
We've got him to say 'down' if he wants to get down, but he doesn't seem to grasp that down=end of meal yet, so normally asks to get down after a single mouthful of food. DH and I are getting sick of hearing ourselves saying 'Sit down'. We are outwardly calm about it the majority of the time, and replace him in his seat calmly each time, but it's driving us both nuts. And I do occasionally snap and shout at him when he's being particularly dangerous.
At nursery they are on small chairs and can get up and walk around when they like (which he does, apparently!). We don't really have that option at home. We did try strapping him in more securely (and using a toddler harness on backwards over the seat straps), but both ended up with so much screaming, and him taking off a layer of skin from struggling out of the straps, we'd rather not go down that route again.
So, any tips on how to either calm myself down about this, or stop him prancing about in his seat?