This report on a Brookings study on the amount of homework students are assigned in primary and secondary schools makes clear what parents already know. It is light, less than one hour a day.
"High school students have an extraordinarily light homework load when compared with international peers, according to the Brookings study, citing a 1995-96 math and science survey. Among students in their final year of public schooling, those in France, Italy, Russia and South Africa reported spending at least twice as much time on homework as American students."
Here is the whole report from the Brookings Institution. (PDF file)