When I began teaching in the 1970s, teachers who marked coursework were paid by the exam boards for doing what was then recognised as the boards’ work for them. This ended with the new conditions of service dictated by Kenneth Baker. I suppose it is no surprise that unions, at the time unpopular because of their campaigns of industrial action, acquiesced in this, but it was a glaring injustice. And it would seem, according to Yvonne Williams (“Doubt over value of exam boards’ services”, Letters, 4 May), that the boards take advantage of this as a way of keeping their costs down. Why do the unions not take up this issue?

Adrian Cosker, Former head of history, Knights Templar School, Hertfordshire.