Environment Canada - acid rain education curricula K-12
http://www.ec.gc.ca/acidrain/kids.html

U.S. EPA - 9 Science Experiments exploring acidity and acid rain
http://www.epa.gov/airmarkets/acidrain/experiments/index.html

U.S. EPA - Several potential classroom activities exploring acid rain
http://www.epa.gov/airmarkets/acidrain/activities.html

U.S. National Park Service - Acid rain curricula for grades 6-8
http://www2.nature.nps.gov/air/edu/index.htm

Merrimack River Valley Investigations in Science (MRVIS)
http://www.necc.mass.edu/MRVIS/MR1_6/start.htm

Texas Natural Resource Conservation Commission - lesson plans for grades 2-7 on acid rain and lesson plans on air pollution for grades K-12.