Søren Thorborg was the son of a parish bailiff. In 1911, he graduated from the teacher’s training seminary in Jelling and took up a teaching position at the Skibby Realskole. In 1912, Thorborg was a member of the Danish gymnastics team that won silver behind Sweden in the Swedish system at the Stockholm Olympics. In the following years, he worked as a substitute at Copenhagen School Administration and as part-time teacher at Baadsmandsstræde School. Contemporaneously, he passed the higher education entrance qualification and continued his studies, taking various courses.
Thorborg also served in the artillery of the Danish Army from 1913-15 and subsequently became a second lieutenant in the reserves. Starting in 1919, he had permanent teaching jobs at the Sølvgade’s, Forchambersvej (1922), Hillerødgade’s (1933), and Emdrup (1943) schools. In 1946, he was promoted to head teacher. He married Petrine Nikoline Thorborg Østrup, with whom he had three daughters and one son.