How many different school boards are there in the US? School boards
mean those that handle public education k-12.

This might be helpful:

"In 1930 there were 200,000 school boards in the United States. Today,
with twice as many citizens and three times as many students in our
public schools, we have only 15,000. Once one of every 500 citizens
sat on a school board; today it's one out of nearly 20,000. Once most
of us knew a school board member personally; today it's rare to know
one."
-- Deborah Meier, writing in American School Board Journal, September 2003 

http://www.illinoisloop.org/boards.html

Thats crazy huh... I heard something like that. Didn't know if anyone
knew the exact number.

Jimmy Carter started his political career by running for president of
his local school board. The idea of public service to the community by
serving on a school board is fading. Too many unsolveable issues from
budget to curriculum to dispiriting notions such as arguing with those
who dislike Mark Twain and evolution.