Background
He was born in Tvedestrand as a son of teacher Andreas Gjelsvik (1863–1938) and Brita Bolstad (1872–1953).
He was born in Tvedestrand as a son of teacher Andreas Gjelsvik (1863–1938) and Brita Bolstad (1872–1953).
He finished his secondary education in Arendal in 1926, and graduated from the Royal Frederick University with the candidate.real.
Degree in 1933—specializing in astronomy. In the same year he was hired as a teacher at Orkdal District Gymnasium. When Vinstra District Gymnasium was established in 1946, Gjelsvik became its first principal.
From 1969 to his retirement in 1975 he was the principal of Stabekk Upper Secondary School.
He was promoted to chairman in 1962, and when the council was superseded by the Council of Gymnasiums in 1965, Gjelsvik continued as chairman until 1969. From 1963 to 1967 he led the Gjelsvik Committee that shaped the "reform gymnasium" in Norway, removing the former rigid division into science or philological courses.
Gjelsvik also chaired the State Textbook Council from 1970, where he had become a member in 1962. He wrote textbooks himself in projective drawing (1946), mathematical geography (1954) and astronomy (1963), and translated other textbooks into Nynorsk.
Gjelsvik served in Nord-Fron municipal council from 1956 to 1960 and Oppland county school board from 1960 to 1964.
In 1968 he was named as deputy chairman of the Broadcasting Council. He died in October 1976 in Bærum.
In 1958 he was named as a member of the national Council of Teaching, which among others was responsible for final examinations in the upper secondary school. He was a board member of Norsk Lektorlag from 1945 to 1950.