yy iggly,
well remembered! we applied to emigrate, but because dd2 has cerebral palsy, the automatic assumption was that she also had a learning disability (whatevah). for canada, you have to prove that you are not going to be a burden on the state (ie a cap on special ed requirements/ social care etc) so we had to get a full assessment detailing her cognitive ability etc etc. there was no way the lea were going to pay for a full assessment because they knew she had no learning disabilities (she rocked up to yr r reading cs lewis
). so we got a private assessment done and used it for immigration (very successfully - i was expecting to have to go through appeal etc). i have no doubt that as she was vs across the board (except processing, which was impacted by her fine motor) the required proof of no learning disability was provided... they couldn't argue, really.
the school here got dd1 tested, because it's a pre-requisite for their (g&t/ able student) coding, and any student working two grade levels up across the board is marked for g&t testing - so they tested her and she scored highly enough to get coded and can participate in the regional programmes for more able children (she is currently being matched with a local community business mentor to come up with external project work that they can carry out over the year)
interestingly, we were told originally that dd2 couldn't access the same programme as her handwriting wasn't two grade levels above her peers (
no kidding! that'll be the brain damage/ fine motor issue
) but on actually reading her wechsler testing, they've decided she can be allowed to type instead...
we've never had ds1 tested. the school suggested it/ wondered about it last year, and the gp has sometimes remarked it might be interesting. school know he's working ahead (if he wants to) but he has more complex issues i think - he's kinda as/asd/adhd/add/odd/ with a heap of anxiety. i'd be interested in seeing his profile
but we are currently toying with removing him from school as he's the square peg/ round hole at the moment. the structure suits the girls but ds1 can't get to grips with it at all. his teachers have just sort of dismissed him as something different/ einsteiney and let him get on with it really, not having the time to find out exactly what/ how to motivate him, and letting him away with it because they recognise he's clever. it's not doing anything for him at all and finding the curriculum v restrictive. the new teacher has decided that more restrictive is the answer (so he won't get any differentiation unless he proves he can answer mind numbing questions they know he knows the answer to) which i kind of agree with, but there's just no way on this earth that ds1 is going to follow through. if he can't see the point in doing something, it's virtually impossible to get him to do it (he just gets distracted by more interesting stuff, rather than any sort of refusal), so that's most of the education system written off in one swoop. 
so, if there's a point to it, i'm in favour of testing. but we aren't quite there with ds1 in the same way that it was 'right' for the girls. and we would only bother with ds1 if we were certain he would stay in school rather than he, which at present, we aren't really.