Very interesting indeed, as are some of his links. Would explain the discrepancy between my two. One dc IDed as G&T practically from day 1 in a primary that used extension. The other, obviously bright but never anything more, totally gobsmacked by 2ry school IDing them as G&T during Y7. (We, BTW, having been considered pretentious by the 1ry school over our suggestions that they were missing something in dc2.) Same 1ry, same 2ry. Several 2ry teachers have commented that dc2 is actually ahead of where dc1 was at the same age. The difference is, I think, that 1ry would say "If you've finished, here's some more/some harder work", whereas 2ry starts from open-ended questions and if you've finished says "have you thought about xyz?"