I've heard from friends that sometimes if a child doesn't get a level 3 at KS1 targets can be set inflexibly going forward?
In other words less than a level 3 at KS1 may translate to a level 4 at KS2? The middle group being taught to lower NC targets than the higher group. Therefore unless you're plugging the gaps at home a level 5 at KS2 will be nigh on impossible to achieve?
I've seen how some lessons are differentiated and there is plenty of scope for the top group to pull further and further away from the others in terms of ground covered. It may be that some in the middle don't have a chance to prove their potential?