A former teacher and football coach at Unity High School in Mendon is facing criminal sexual assault and aggravated criminal sexual abuse charges involving a student.

Geoff Dalton, 33, was arrested Sunday in Quincy by U.S. Marshals and Adams County Sheriff’s deputies at a family member’s residence after a warrant was issued following a monthlong investigation. According to charging document information, the two offenses allegedly took place between January and May 2007 while Dalton was a Unity High School teacher and the victim was a student.

Dalton is teaching communication arts at Harrisonville High School in the Kansas City area this year, and he also is an assistant football coach.

Jill Filer, director of communications for Harrisonville High School, said the school learned of Dalton’s arrest Monday. He is not teaching at this time, but Filer declined to comment if Dalton was on paid or unpaid leave.

“If such an allegation is made regarding a current employee, the district will not permit the employee to have contact with the district’s students while the allegations are pending,” Filer said.

A letter to parents was sent home with students Monday, Filer said, along with a copy of an online Herald-Whig story about the arrest.

Dalton posted 10 percent of a $30,000 bond. Dalton has an initial Adams County court appearance scheduled for Dec. 8.

Dalton was the football coach at Unity from 2005 to 2007, posting a 3-24 record. He was instrumental in organizing funding for a proposed new weight room at the school and improving outdoor facilities, though none have been built. He also was the head track coach during his time in Mendon.

The Unity School Board accepted his resignation during its March meeting.

“We’ve been cooperating with the investigation the entire time,” Mendon Superintendent Diane Robertson said.

Dalton previously coached at Alton Marquette, Jacksonville Routt and Louisiana, Mo.

Dalton is a 1993 graduate of Quincy Notre Dame High School and was a three-year letter winner in football at Culver-Stockton College in Canton, Mo., where he graduated in 2000.

Criminal sexual assault is a Class 1 felony punishable by up to 14 years in the Illinois Department of Corrections. Aggravated criminal sexual abuse is a Class 2 felony punishable by up to seven years.

Harrisonville is located about half an hour south of Kansas City in Cass County. Harrisonville High School has an enrollment of 843 students, according to the school’s Web site.

— rhart@whig.com/221-3370