Back when Hurricane Sandy pummeled the east coast, I offered to give people who donated to the Red Cross a free copy of my Math Guide. The offer generated a few bucks for charity, and I got to give away some books to people with generous hearts. I was pretty happy with how it worked.

I don’t spend a great deal of time talking about why I started this site because I don’t want to bore you, but a large part of my motivation was that I believe in a level playing field. I don’t think access to good test prep—a proxy for access to education in general—should be limited by geography or wealth. The Internet provides an opportunity to mitigate both barriers, and 2+ years and thousands of posts later, here we are.

But by the time students want or need access to good SAT prep, they’ve already completed the lion’s share of their primary education. I do SAT prep because that’s what I’m good at, but inequality in education spans all grade levels, and I’ve been thinking a lot about ways I can leverage this site to make a difference for students long before they start thinking about the SAT.

Last month, I decided that I’d start donating 10% of the royalties I receive from Math Guide sales to education-related charities. One charity I really like is DonorsChoose.org, because it lets me decide which classrooms to donate to. (I favor projects involving early math education in low-income public schools.) Today, I’ve decided to take things a step further.

If you (or your parents) donate $50 or more to a project on the PWN the SAT DonorsChoose.org Giving Page, I’ll give you a free copy of the Math Guide (US residents only). To participate, simply make your donation at the link above, then forward your receipt and your shipping address to mike@pwnthesat.com.