23 minutes ago, Anna N said:My memory told me it was 1/3 of a pint but I couldn’t find any confirmation and wondered if I had mis-remembered! Thanks.
https://spartacus-educational.com/ED1946.htm
In fact, although schools had been empowered (but not required) to issue free milk in 1921, the universal standard free 1/3 pint wasn't introduced until 1946 under the 1946 School Milk Act. It lasted until 1968 when it ended in secondary schools then 1971 in all schools. To this day the then Secretary of State for Education and Science, Margaret Thatcher, later Prime Minister, is known widely as "Thatcher, the Milk Snatcher"!