I'm not (and never have been) a primary school teacher, but isn't it the case that the younger they start, the easier they'll find it?
I'm sure I remember parsing sentences at infant school (or it may have been juniors, but in any case I'd have been younger than 11). I probably quite enjoyed it, but I was that sort of child at that age . My enthusiasm was knocked out of me soon after, but that's another story. Little ones pick up language really easily, and can learn multiple languages with very different grammar systems. It can be a lot more difficult for adults, though.
I think a lot of adults are scared by the changes in terminology (fronted adverbials, anyone?) and I have no idea why that was necessary, as it makes it very difficult for anyone other than teachers to discuss grammar with children.