The lede to this article says it all:
Eli Broad and Bill Gates, two of the most important philanthropists in American public education, have pumped more than $2 billion into improving schools. But now, dissatisfied with the pace of change, they are joining forces for a $60 million foray into politics in an effort to vault education high onto the agenda of the 2008 presidential race.
There were quite a few proponents or education choice who warned Broad and Gates that they'd be disappointed with the results of their investments. Yet their response is to spend $60 million more to nudge 2008 presidential candidates to promise even more spending on public schools.
Far be it from me to tell Messrs. Gates or Broad how to spend their money, but I'd imagine that $2.06 billion would have bought a lot of scholarships for poor kids to attend private schools that have proven records.