Armstrong graduated from Blue Earth Area High School in 1990, and attended both Gustavus and MSU-Mankato. He graduated from MSU in 1996. That year he accepted his first teaching position in Chatfield, MN. While in Chatfield, he was on staff for the Gophers third state football championship. In 1997 and 1998, he coached linebackers at Gustavus Adolphus College in St. Peter. Then in 1999, he joined the Blue Earth Area High School staff. He teaches Biology, Anatomy and Physiology, and POE. He currently is the defensive coordinator of the varsity football team at BEAHS. In the winter he leads the B Squad Girls' Basketball team, and is the head golf coach for the boys' team in the spring.
His wife is also employed by Blue Earth Area Schools as a social worker in the Middle School. The two have two girls at home, Téa was born first and is the older sister to Addison. Rounding out the family are Gizmo and Carmin their two Shih Tzu dogs. Some of his hobbies include reading, golfing, and hunting.