I am flagging this precisely because I believe the Hacker School experience is valuable and yet you offer a sexist and discriminatory grant to women.I'll outline this for you as clearly as possible.
Fact: a small, but significant, group of engineers in our field are sexist. They post GIFs that make women uncomfortable, call women "conference hos," and do otherwise lewd or inappropriate things.
Fact: as a result, women are uncomfortable working as software engineers. We know this because many blog posts state this discomfort explicitly. Your niece, unfortunately, may experience this if she decides to work as a software engineer.
Fact: we see similar grants for college attendance; these grants attempt to fight various socioeconomic factors ("old boys networks," among other things) that may prevent underrepresented groups from attending prestigious colleges.
Would you feel comfortable offering such a sexist grant to men only?
Obviously not. Why? Because, as the above facts illustrate, this grant attempts to address the sexism women face in our industry.
The Hacker School team can't drive around and hit every sexist idiot with a bit of reality, but they can try to provide an antidote to this sexism by (a) alleviating financial concerns for aspiring women engineers, and (b) providing a guaranteed non-sexist zone for them to practice their craft.
I can see how one might argue that this grant selects on behalf of gender, thus giving it an "affirmative action" flavor. That person, however, might want to present an argument slightly more nuanced than "THIS GRANT IS SEXIST ZOMGGGGGG," like you've done. You may want to try again.
(Also, a fact for those finding this via Twitter: Jerry does not represent the entirety of HN. (I'm waiting for Danilo Campos to join in, he usually whacks people with a sanity stick when it comes to misogyny in tech.))
(Also also, while I believe with all of my being that you're wrong about this, I didn't downvote you, because your comment fosters some good discussion (in a roundabout, totally unintentional way).)