It is often asserted that UK school-leavers know less grammatical terminology than in earlier years. However, objective data on this supposed phenomenon are somewhat scarce. The study reported in this paper aimed to see whether and to what extent knowledge about language (KaL) has declined over three decades, and how this might relate to university studies and the English school-leaving examinations known as A-level. We analysed data collected in a test-based survey of UK university undergraduates and compared them with a similar test-based survey conducted in 1986. We also put the studies in context by comparing the performance of UK home students with that of students in and from other countries. In addition, we analysed recent pre- and post-test data on whether courses of instruction in grammar improve undergraduates’ knowledge of grammatical terminology. Our results show a general reduction in school-leavers’ knowledge of grammatical terminology since 1986. Moreover, UK students have a much weaker knowledge than do non-UK students. Studying a foreign language leads to somewhat better levels of KaL, but this is not true for English language A-level. However, our results confirm that university-level instruction does improve awareness of and ability to use grammatical terminology. We end by discussing the value of KaL.