US schools do not, on average, seem that underfunded to me. Look at http://nces.ed.gov/programs/coe/indicator_ifn.asp to verify that the USA averages more per student than most industrialized countries. Even if you correct for GDP, the USA is not that bad.

That said, money is distributed very unequally. There are lots of very underfunded schools - with many in California. See http://datacenter.kidscount.org/data/acrossstates/Rankings.a... to see why.