MorethanPP
It has always been possible to report children as Level 6 using teacher assessment at the end of Year 6. This year, for the first time in many years, there has been a decision to set Level 6 papers for children to sit.
My DS has just taken them. Not because he is going to a selective school - he's going to our local comprehensive. Not because his school is selective - it's a bog-standard state primary. But because he has been working, particularly in maths, at level 6 this year.
On the negative side, some schools have been entering Level 5 children 'just to see if they pass the level 6' - thus reinforcing the whole 'they may test at a level but that isn't backed up by their day to day class work so it's not real' perception from secondaries.
On the positive side, for those children like my DS where they genuinely are working at Level 6, having some kind of benchmark test MAY mean that Level 6s given by Year 6 teachers have a little more credibility in terms of a starting point in year 7...
I'm guessing that the negative side will win out, given the approach to level 6 papers reported on MN. However, whatever happens in the test, it has encouraged DS's Year 6 teachers to continue to teach new mathematical concepts to the most able throughout the year, rather than concentrating on up to level 5 stuff 'because it is what will be tested'.