Hacker School is not what you'd call a school — there's no curriculum or tuition at all. Rather, it's a community of people with a wide range of coding skills, from near-beginners to very advanced professionals.
The activity of this community is intense, self-directed computer programming, in individual and sometimes group projects. Not only the coding but the choice of projects is self-driven, too. Admission to the community is highly competitive, but let me say again that participation has no dollar cost. There is a cost, though — a high one: working and thinking hard about the processes at hand. It would be easier just to pay some money and not necessarily engage one's mind. Try that elsewhere, not at Hacker School.
The purpose of attending Hacker School is to become a better programmer, which participants do usually by building things and sometimes through collaborative programming activities. The organizers have as two of their high-level goals to increase demographic diversity in the programming world and to promote their vision of an inclusive and safe workplace.
The organization makes money as a recruiter, placing participants in its network of companies and being paid by those companies.
I have attended two three-month batches, and the experience entirely changed my life and direction. My background is unlike that of most other participants, but it's fair to say that I would probably never have found a good job as a programmer if not for Hacker School. As it happened I found work outside of Hacker School's network, so they did not make a penny on me, and yet they've been generous and helpful to me in my job search, writing letters for me and making introductions and so forth, every step of the way. Techendo is currently (20150103) trying to answer the question "are dev bootcamps a scam?" Let me say clearly that Hacker School is anything but a scam. It is a visionary movement in the coding world.
Hacker School is really not to be compared to any of the dev schools or coding bootcamps around — it belongs to a wholly different phylum. Techendo includes it in the Development Schools category I imagine by default, but it doesn't really belong there.