Goodness, the poor APS head appears to be getting some stick! I've never found him to be "odd" or quirky or even mildly eccentric ! Lovely man and genuinely proud of his lads. Hugely academically-minded , yes, also very switched on to current teaching methods and keenly aware of how children's minds work. And ,yes, 'old-fashioned', but insisting on good manners and conduct isn't a bad thing is it? If the boys vote for extra playtime with him as a reward for good behaviour, doesn't that tell you how attuned he is to them? [I do know of one miscreant ds threatened with being sent to the head's study, who reacted very cheerfully and said he'd like to go please ...not even thinking it could be a punishment. On his return he reported that they'd had "a very nice chat"]
As to APS entry rates for grammar schools, please remember that the school isn't selective at entry level. They work with the material they've got. I write as someone happy with the ds progress there but not confident that he's 'MGS material'. I know lots of parents (ok, most) see grammar school entry as the holy grail but really it isn't the thing for all children. We're lucky to have lots of very well regarded secondary schools in the area and I'd investigate them and see which would actually suit you.
The only way you can guarantee entry to eg. MGS is to circumvent the exams in Year 6 and that means paying, and continuing to pay to 18. (That's the price of a small street in some not too distant places). It may or may not mean that your ds is in the magic top third of MGS achievers. It's up to your child's performance on the exam/ assessment day and it's sad that it comes down to that, but there it is.
RCmum have you thought of asking for a breakdown of the entry figures or where the non-grammar boys went or why? Just a thought but 80% (that's 32/40 boys, remember) seems a high percentage to me
Just try to remember that the most important thing is for your ds to enjoy his education not feel under constant pressure to achieve some unattainable standard.