I like B maj as a first scale too
Technically, I like to do a few scales similar
before introducing contrary, as this avoids the common problem of the elbows swinging out like chicken wings whenever the thumbs go under.
We play on the black keys by ear quite a bit first - eg Frere Jacques starting on F# , with the LH starting and RH imitating in canon is a good challenge ( for adults as well as younger beginners). Maybe I'm lucky, but most students crack this in a week . This can lead nicely into F# major similar - quite hard to get wrong, as the black key pattern is so helpful, and the thumbs meet on the 2 white keys. This is usually the first 'hands tog' scale we do. Then D flat major, then maybe B, and E - and then E major contrary.
Then we 'scale' up the white keys only - starting anywhere except
C, to get used to the sound of different patterns. Fingering : 1st using 12, 12, etc with elbow still
- when that's getting smooth then 123, 123 - and finally 1234. Only then do we focus on 'standard' fingering for white key scales, and do clusters of 3 4 3 5 up (and down) the keyboard, emphasising the use of the wrist to change position.
When introducing a new scale - eg A maj, we'd do the clusters starting on A with white keys only, and then work out which black keys are needed. Then similar, contrary, various rhythms, and (eg) crotchets in LH, quavers in RH and then swap over.
Of course, we'd only spend approx 5 ish mins on this at the start of every lesson, before getting on to some real repertoire. It's all developmental and cumulative. Hopefully.
I can't imagine starting hands tog scales with C maj and then gradually adding #s. Not only is it very tricky technically - the lack of black keys makes it hard to kep track of where the thumbs should come!
Phew - anyone would think I was keen on scales or something! I'm not - it's only a means to an end. And there's no point in doing them before some basic finger control's been established, so I wouldn't introduce too many too soon.
Oh - and I try not to look at the AB scale syllabus too much, to see which scale is at which grade, as I think they've got it all a bit back to front. ( Well, of course I do check before they do an exam, but that doesn't happen too often!)