The aim of this study is to investigate how the Swedish language proficiency of pupils in vocational programmes in 1977 was measured and assessed with the aid of a national achievement test, and to investigate whether vocational pupils today, in 2014, have similar language proficiency to that of pupils in the 1970s. The study also discusses how the design of the national achievement test from 1977 reflects the view of knowledge that prevailed in society and in the policy documents. The material for the study consists of a total of 75 national achievement tests, 40 of which were taken by pupils on a vocational programme in 1977 and 35 by pupils on a vocational programme in 2014. The national achievement test consists of two parts, the first of which focuses on isolated elements of language proficiency, while the second involves free text production. The material was analysed quantitatively in accordance with the correction material from 1977. The tests were also studied qualitatively through a close reading and analysis of content and text structure, correct language usage, and style. The pupils’ results were then quantified according to the assessment scales from 1977. The results of the study show that both groups of pupils had difficulties with many parts of the test. The pupils from 1977, however, performed better on both parts of the test than the pupils from 2014. The pupils’ often inadequate results in the test raise questions about the design of the national achievement test from 1977 and vocational pupils’ proficiency in Swedish.