You continue to try to locate the problem in middle school while removing any means, direct or indirect, of addressing it. As you observe, speaking at a conference is beneficial to one's career; fostering female participation in conferences advances the careers (and visibility) of females in the field generally. You don't need to bus in a bunch of twelve year old girls and point at the female speakers. You just need the field itself not to look so totally male. In medicine, rising female participation outside of nursing has demonstrably accelerated the rate of female participation since the 1970s. The same can happen in the rest of the STEM field. It's obviously not a turnkey solution, but is valuable as part of a general attempt to diversify the field.
You continue to try to locate the problem in middle school while removing any means, direct or indirect, of addressing it. As you observe, speaking at a conference is beneficial to one's career; fostering female participation in conferences advances the careers (and visibility) of females in the field generally. You don't need to bus in a bunch of twelve year old girls and point at the female speakers. You just need the field itself not to look so totally male. In medicine, rising female participation outside of nursing has demonstrably accelerated the rate of female participation since the 1970s. The same can happen in the rest of the STEM field. It's obviously not a turnkey solution, but is valuable as part of a general attempt to diversify the field.