Convinced that the exam system for 16-year-olds was out of date, he helped to develop the CSE and then the GCSE. He championed coursework and dual certification syllabuses and, although these were later axed, he always upheld the principles behind them.
Terry became treasurer and later chair of the National Association for the Teaching of English, strengthening its finance, publications list and membership. He also chaired the International Federation for the Teaching of English.
In 1986 he became inspector of English in Brent and helped to design the first national tests in English for 14-year-olds while on secondment at the London Institute of Education. He wrote numerous articles, took part in conferences, lectured throughout the country as well as abroad and contributed to books on education.