(AP) — A former Omaha middle school teacher has been sentenced to nine to 14 years in prison for his inappropriate relationships with girls he taught.

A Douglas County District judge sentenced 36-year-old Shad Knutson on Wednesday. Prosecutors say Knutson had inappropriate relationships with girls ages 13 to 15 from 2008 to 2010 while he taught at Nathan Hale Magnet Middle School.

Knutson was convicted in March of using a cell phone to commit sexual assault and child abuse for asking a girl for lewd photos.

Prosecutors say Knutson exchanged some 27,000 messages and calls with one girl. He was acquitted of counts involving three other girls.