"Two sixteen-year-old lads were each fined 10s at Dundee Juvenile Police Court to-day, when they admitted consuming in a public house 2 pints of beer and two quarter gills of whisky. "
Dundee Evening Telegraph - Saturday 15 January 1944, page 2.
The boys were both younger and drank considerably more than the girls. They were fined, but not put on probation. Mmm.
I'll see if I can find more cases of underage drinking in the archives.