Along the same lines I can point out 2 good reasons boys are generally driven in that direction.
1. Boys are into video games - for the very same reason that big gaming is targeted at boys and that the majority of players are male. Those gamers are into computers and the possibility of coding future games, so they go into computer science. Girl gamers are starting to become a little more common, and their representation in computer science might increase organically if everyone just left it alone.
2. Boys like to build things - along the lines of Lego, blocks, and carpentry. Boys dominate "shop class", but I don't recall any big push to change that. OK, the shop class I had in high school did have a fair amount of girls in it, so maybe that's not a big concern. The building enjoyment flows into programming because the program that comes out at the end was "built" by you.
There are some toys aimed at getting girls into building things, so that's a good thing as well. I don't know that threatening funding is the best plan. That puts all of the pressure on the teacher or school to try to drive girls in that direction (and makes me think that down the road "unwillingly" isn't out of the question, or granting a passing grade for sub-par work just to keep the numbers up). Games that girls are interested in and getting girls into "building things" at an earlier age is where the attention needs to be. So that lies more in the parents, and asking parents to make their daughters good little cogs isn't likely to garner much traction...which is why nothing has worked so far.