This study describes the validation of a reading assessment developed for speakers of Scottish Gaelic, an endangered language spoken in Scotland. The test is designed to investigate the areas of reading for understanding, reading errors and reading speed. This study will present the data on a group of Gaelic/English speakers on both the Gaelic and the English version of the test and of a group of English speakers on the English version of the reading test, aiming at comparing reading abilities in children attending a Gaelic medium education (GME) and children in English medium education (EME) living in the same urban area. The paper reports two studies. The first study presents data on 77 children bilingual in Gaelic/English recruited across four levels of primary school on reading in Gaelic. The second study looks at the performance on a version of the test adapted for English, comparing the performance of two groups of children (bilinguals Gaelic/English and monolinguals English) on several linguistic skills, including sentence comprehension and reading. About 40 monolingual English subjects in EME, living in the same urban area, were administered the English version. The reading abilities of the children attending EME and GME schools were comparable, supporting the idea of no disadvantage on reading from attending a school with the medium of a minority language. If differences were found, these were in favour of the bilingual Gaelic/English children, who attained better results in all linguistic tasks in English in the older groups.