All engineers I know who worth their salt acquired their skills mostly through self-education and lot of practice, and the process was gender-independent. I don't think 'boys-are-not-allowed' classes will put any of the participants closer to professional careers in coding.
Its related to the validity of your "observation", in that, if teaching to code is not a female-dominated activity, your "observation" that she chose a female-dominated activity is false.
> All engineers I know who worth their salt acquired their skills mostly through self-education and lot of practice, and the process was gender-independent
Oh, well, if we are going to do dueling anecdotes, all programmers (even if including that population within engineers is proper, there are a lot of engineers outside of that group, and I'm not talking about them, since this is about teaching coding, not teaching engineering in some general sense) worth their salt I know started by being taught by someone -- usually in school or a similar environment, though sometimes tutoring by a family member with experience in the field played a similar role -- at a fairly young age, and then, after developing an interest there, proceeded to choose further education -- both guided and autodidactic -- and lots of practice.
Well, if you insist on reductio at absurdum, let's continue on. Teaching to code in gilrs-only classes is obviously not a male-dominated activity, would you agree on that?
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This side of the pond, it's fun to observe how Americans try to integrate minorities into bigger groups. The usual tools are: "positive discrimination", ban on open discussion and general patronising attitude on the side of a majority. Because that worked just oh so well with racial minorities.
Last thing women need is your 'knight in the shiny armour' stance toward them. Just treat them as equals, and they'll beat you in your own game once interested enough. It's that easy.
(And, yes, I'm a married man; a father of a beautiful, independent and ambitious daughter; and a hiring manager, with 100% women applicants being hired so far: for being great engineers, albeit a bit unconfident, hence only applying when absolutely sure they're up for the job).