He joined the Miners' Federation of Great Britain and the Independent Labour Party and also attended classes arranged by the Workers Educational Association.
In 1916 he returned to the coal fields and began teaching classes in industrial history under the auspices of the Aberdare District Miners' Federation.
When the NCLC absorbed the Plebs in 1927 Starr began to find his position in the group untenable and immigrated to the United States to become an instructor at Brookwood Labor College in Katonah, New York.
Along with the Horrabins, Starr briefly joined the Communist Party of Great Britain during the early 1920s, but soon left, unable to stomach the group's discipline.
In America, Starr continued as an instructor at Brookwood until 1935, when he became educational director of the powerful International Ladies' Garment Workers' Union, a position he kept until 1960.
After retiring from ILGWU he represented the International Labour Organization in Singapore and East Africa and continued his Esperanto advocacy.
The information for this article was taken from Richard Lewis, STARR, Mark (1894-1985) WORKERS' EDUCATIONIST, The Dictionary of Labour Biography, Vol.