Ladyquinoa/ mrz:
You both raise some really good points & contradictions in the system.
In an ideal world (a world like mrz's situation) a L6 in primary = L6 in secondary; however, that isn't every school in England. It should be perhaps, but it isn't. I think we have to accept that cramming Y6 classes for SATs/ endlessly taking past papers/ giving class SATs workbooks/ etc.... (very much the situation for DD1's Y6 class) may be somewhat skewing results; not in the sense of them having passed that threshold on the L6 SATs paper - but in the sense that a new Y7 having scored L6 on SATs in such a way may need a lot more work at that level, maybe even L5 to consolidate skills/ knowledge.
I think we also have to accept that dovetailing L6 teaching in primary by incorporating secondary level teaching (through extension classes, regularly having a secondary teacher teach a subject like maths, etc...) is rare (i.e. not the norm in English primary schools).
and...
maybe given that L6 is the 'new L5' - maybe the government needs to facilitate that bridge at L6 where a primary student has exceeded mainstream curriculum content (L3 - L5) and for their own benefit should be stretched to L6 (secondary) curriculum level work. (and maybe the government needs to accept for the greater good - they need to fund this).
Certainly I have a able mathematician in DD1 - who would enjoy working at L6, but in all sincerity her school is so wrapped up in getting about 1/2 of her Y6 class to L4, that the upper ability group is being taught by a Y2 teacher and endlessly reviewing things. She's bored out of her skull. I fear that is not an unusual scenario - and is a waste of potential.
And that is the reality playing out in school after school here in my little corner of England.