When was it first mandatory for children to go to school in Britain?

Strictly speaking, never. All the legislation on the matter relates to compulsory education, not schooling - but there is one exception. 1870 - School Boards, in areas where they existed, had the option of making education compulsory between ages 5 and 11. 1876 - This was extended to areas without School Boards. 1880 - Education from 5-11 made compulsory thoughout England and Wales. Note that the Factory Act of 1844 required large scale employers to provide part-time schooling for child employees aged 8-13 (later 14). In fact, compulsory education has often been widely taken to mean compulsory schooling.