From 1916, Nielsen taught at the Royal Academy where he became director in 1931, shortly before his death. He also had private students in his earlier days in order to supplement his income. As a result of his teaching, Nielsen has exerted considerable influence on classical music in Denmark. Among his most successful pupils were the composers Thorvald Aagaard, remembered in particular for his songs, Harald Agersnap, both a conductor and orchestral composer, and Jørgen Bentzon who composed choral and chamber music mainly for his folk music school (Københavns Folkemusikskole). Among his other students were the musicologist Knud Jeppesen, the pianist Herman Koppel, the academy professor and symphony composer Poul Schierbeck, the organist Emilius Bangert who played at Roskilde Cathedral, and Nancy Dalberg, one of Nielsen's private students who helped with the orchestration of "Aladdin". Nielsen also instructed the conductor and choirmaster Mogens Wöldike, remembered for his interpretations of Baroque music, and Rudolph Simonsen, the pianist and composer who became director of the Academy after Nielsen's death.