I don't know whether the lack of replies so far to your query is due to the post title, as I know nothing at all about "pre-testing". However I have had two boys pass through the ages of 10 to 13 plus observed many other friends' boys.
I don't think you can separate out the physical development, as the variation in the timing of that affects a lot of other things. 10 year old boys of my acquaintance are often very lively, cheeky (sometimes), obsessed with their special interests (football, cars, chess or whatever), happy to play alongside friends who are mostly other boys, oblivious to what they wear unless it's a favourite t-shirt, no idea about washing, put up with school as a necessary evil, like to be doing things rather than chatting, regard girls as an alien and slightly puzzling pink species... They won't necessarily do what they're told but ignore it because they're busy with something more interesting (involving mud..) and possibly get up far too early at the weekends
By 13 some of them are still like that (!): but some have grown up faster physically, have become a bit more unco-ordinated as their brains fail to keep up with their increased gangliness, they may have a wider circle of interests and friends including girls and be happy to chat, more conscious (some of them) of wearing trendier clothes, probably still regard school as a necessary evil, but able to work hard at something that interests them (music, sport, raising chickens etc). They might also have started slamming doors, using deodorant, having showers rather than being put in the bath, causing their parents to despair etc etc.... They may not want to get up at all at the weekends...
Not sure if this helps at all! You have so many options it seems that it is impossible to be sure you can choose "the best" - but if they are bright boys, with a supportive family and circle of friends, how about relaxing a bit and looking for something that is "good enough" and will enable you to enjoy watching your boys as they grow up into stroppy teenagers and eventually talented young men. Their lives will not be blighted forever if they don't go to the "top" schools - no school will suit them perfectly, but constant anxiety about whether somewhere else would be/ have been "better" in some way won't help them feel settled.
Best of luck with all the decisions