 He taught in Accrington until 1960, then moved to Northampton, where he taught at St Mary's High School.He also joined the National Association of Schoolmasters and was elected to its National Executive in 1966, remaining on the body after a merger formed the National Association of Schoolmasters Union of Women Teachers (NASUWT).In 1976, Smithies was elected as vice-president of NASUWT, then, later in the year, as the union's assistant general secretary.