PHOENIX (AP) _ Gov. Janet Napolitano signed into law Tuesday a ban on the sale of junk food in Arizona's elementary, middle and junior high schools.

The measure, which takes effect in 2006, is aimed at candy, soft drinks and other sugary or fatty snacks. It would not affect sales of junk food before or after school hours, such as during athletic events.

The bill was backed by health groups and the state school superintendent as a way to combat obesity and promote good nutrition. Critics called it an intrusion on school districts' authority.

In a compromise, high schools were exempted from the ban.