The latest Obama campaign ad is about education policy and it levels two accurate accusations against Mitt Romney. One is that Romney has said class size reduction policies aren't a good way of improving school outcomes, and the second is that the House GOP budget that Romney supports implies huge cuts in federal education spending:
On the latter point, I have no real complaint. Romney's put out a K-12 education plan that contains some interesting ideas and some problematic ones but the big story really is that his budget won't leave much money for anything. But on class size while Obama's claim is perfectly true, it's a strange allegation to level in light of the fact that Education Secretary Arne Duncan believes the same thing.
I used to work at the very Obama-friendly Center for American Progress and the education team over there agrees with Romney and Duncan about this. It's not that "class size doesn't matter" exactly. It's that at most plausible margins, it makes more sense to invest money in hiring and retaining the most effective teachers rather than in simply adding more teachers. The fact that Obama agrees with Romney about this is presumably why Obama's education policies have focused on investing money in teacher quality rather than in maximizing the number of teachers. As Lenin said, better fewer but better. This is one reason I'm not thrilled with the concept of ad "fact-checking" items. There's nothing inaccurate about Obama's ad, but accurately accusing Romney of holding a (correct) view that Obama also holds isn't really something that deserves a thumbs up.