DES MOINES, IOWA -- A new state report says Iowa's courts have not been levying increased penalties for drivers who illegally pass a stopped school bus.

Kadyn's Law was passed by the Iowa Legislature in March and signed into law by Gov. Terry Branstad. It's named for Kadyn Halverson, a 7-year-old girl who was hit by a pickup and killed in 2011 while walking to her bus. The driver of the truck, Aaron Gunderson, was sentenced to 15 years in prison.

The law requires a minimum $250 fine. 

The Associated Press reports a study by Iowa State University shows 65 percent of those convicted of school bus violations were assessed a lower fee.

The study was conducted between Aug. 15 and Oct. 31, and looked at a total of 162 convictions.

The Associated Press contributed to this article.