A popular science teacher at Riverton High School in Sangamon County was found unresponsive by a school official at the high school Saturday morning. David Dressel, 51, was pronounced dead at 11:05 a.m. An autopsy was scheduled for Monday, and his death is under investigation.

Dressel, who taught chemistry and physics, was at the high school to supervise Saturday school. Riverton school officials commented that he was a positive presence in the high school and for the entire community. He was in his fourth year of teaching there.

Dressel's wife, Heather, is a special education teacher at River...