Not to speak ill of philanthropy, but...
Seems self-serving in a way to target this at the greater San Francisco area where there has been a lot of class division recently over the effect all the dotcom millionaires from Google, Facebook, et al have been having on property values and the cost of living in the city. Trying to curry a bit of favor with them, perhaps?
There are a lot of places in the US with far greater need of aid for public education. Like across the bridge in Oakland, let alone places like Detroit. I'm sure all the Facebook employees who came too late to partake in the IPO party will appreciate that he's improving the public schools (many of the dot.com millionaires will send their kids to private schools)
Its his money, and he can do with it how he pleases, but he's not exactly getting the best bang for his buck versus the efforts of someone like Bill Gates. I may not admire his business practices, but he's got the right focus in his giving - results ahead of personal gain.