School-age underwear

When I started my formal  education apart from the question of uniform which was kept purposely simple in Infants and a bit more mature in Juniors, it was usual to put us into interlocking vests and Y Fronts usually white or pale blue given our school unlike some hadn't formal underwear rules.
Thy were normally made from cotton, sometimes fully covered, other times what was called 'Stringed'  literally criss-crossed except for the actual Y fronted bit and a bit of a religion given the fuss made about making sure we couldn't get cold from the slightest gap.
Later on subject to 'school rules' motifed briefs started to creep in with colourful designs and logos such as 'Concealed Weapon' came out, the latter causing much mirth amongst us although I was very much a traditionalist preferring white Y fronts.