U.S. teachers say they cannot show the environmental movie "An Inconvenient Truth" to their students because of a policy against endorsing projects.

Daily Variety reported Monday the National Science Teachers Association declined the offer by the film's executive producer, Laurie David, to distribute 50,000 copies of the controversial Al Gore global-warming film to its members.

David, bewildered by the refusal to accept the DVDs, wrote an op-ed in the Washington Post where she argues that that the teachers association had accepted contributions from ExxonMobil, Shell and the National Petroleum Institute, among others, where a "shameless pitch for oil dependence" was alleged.

The association denies the characterization.

Not to be detered, David will offer the film to teachers via the Web site participant.net through Jan. 18 on a first-come, first-served basis.

Copyright 2006 by United Press International