Do American teenagers spend more or less time on homework now?  

Anecdotal information seems to indicate that the amount of homework
that American high school students have now is greater than ever
before, but i would love to see statistics that prove or refute that.

I am looking for statistics on hours spent doing school homework
amongst American high school students since compulsory education began
in the late 1930s.  Ideally, i would prefer data per decade although
any data that might compare now with the 70s or 50s would be fine.

I was not able to find decade-by-decade figures since the 1930s, but
I've gathered links to some material that I hope you'll find useful.

http://brookings.edu/gs/brown/20031001.pdf

http://www.naesp.org/ContentLoad.do?contentId=1212

http://www.findarticles.com/p/articles/mi_qa3696/is_199710/ai_n8776075

http://homeworkhelp.aol.com/prccanvas?id=20060207160209990001

http://www.amazon.com/gp/product/0807042196/sr=8-1/qid=1141007452/ref=pd_bbs_1/102-3885032-1953725?%5Fencoding=UTF8
includes a chapter on homework in a historical perspective that
describes qualitatively how the launch of spuntnik changed us from a
nation where "in 1901, homework was legally banned in California" and
in the 1930s it was viewed as a health hazzard, versus the 1987 time
magazine call that "'racheted up the pressure to get tough again' on
homework"