I'm a STEM ambassador, and we are regularly asked to go to schools and careers events to talk about what we do. STEMnet provide this as a free resource to schools and volunteers provide their time freely.
Saying that it is still down to individual schools to ask for this.
I remember when I was choosing my O level options. I'd picked all three sciences and the careers teacher asked if I was really sure I wanted to do that as 'It could be a bit difficult for a girl'.
I then had to point out I thought they were really easy and much easier than Home economics (which is what she taught). Things do seem to have moved on in that respect thankfully, but I still come across girls who think engineering is a mans job.