I think the levels are not the simpliest to understand, in particular it is hard to see whether if your dc is a 4b whether that is good for their age or hopeless.
Also in year 2, I thought it was quite obvious year 2=2b average. Makes sense. But then it took me a bit to realise that they then weren't expecting to get 6b in year 6, and 9b in year 9.
I sort of understand the saying each school setting their own, because different schools use them in different ways, so it looks consistant across the schools but isn't.
For example you always get a few people on here saying they know people in year 2 who got a level 4. Well I don't know any schools round here that would test for that.
A group of our local infants and juniors get together to moderate year 2 marks together to have some consistancy when they go to the same juniors. I know one school refuses and their results don't seem to match the other schools if that makes sense.
I think levels can make a proud parent think their dc is doing better than they are, or a nervous parent think they're doing worse.
If I take my dc's school, they give a list out of "Expected level in year 3 3c-3b, etc." Problem has been at times that some parents think if they've got a 3a, or in some cases a 3b, they are a total genius and are outstanding at the top. Being my 3rd dc I now know that they give up to 4c in year 3, so 3a is good, but it doesn't make the top.
Equally well I've seen parents panicking because they've got a 3c and thinking they'll be in a class at the bottom on their own, when actually they're doing okay.
You then have the time when your dc just scrapes a 3a in one year and is just at the verge of going up to 4b the next year, so apparently has made only 1 sublevel progress. However they really have made almost 2 sublevels.
I quite like the way dd1's secondary does it which is a points system which equates to levels. There's about 3 points per level, plus they give you the range of points in the (very large) year. So when you get one subject that they've only got half what they ave in the other subjects you can look and see everyone is getting less, which puts things into context.
But I have to admit I was quite pleased that the schools here did still give levels, because it's taken me ages to get to grips with them. I think it;s better then this exceeding/expected etc.