A 24-year-old registered sex offender from Harvard pleaded guilty Tuesday to loitering near a school and was sentenced to four years in prison.

In exchange for his guilty plea, prosecutors agreed to drop a charge of aggravated criminal sexual abuse against Jesse Dickson, of 23802 Chemung St., which alleged that he fondled a 15-year-old girl in Wonder Lake in 2006.

Dickson was arrested in November 2006 for allegedly loitering near and socializing with students from McHenry West High School. The girl who he is alleged to have abused was one of the students with whom Dickson socialized at a gas station near the school, police said.

Dickson was convicted in 2000 of criminal sexual abuse of a child younger than age 9 in Arizona. As a registered sex offender, he was ordered to stay clear of school grounds.

Because of his criminal history, the charge that he pleaded guilty to was punishable by up to six years in prison.

With good behavior and time already served, Dickson would have to serve only about 15 months of his sentence.