noun
school commute hat
A hat worn by kindergarten or primary school children when walking to and from school, often part of the uniform and sometimes color-coded by grade.
小学生が黄色い通学帽をかぶって登校している。
Elementary school children are walking to school wearing yellow school commute hats.
制帽 is a general school uniform cap, while 通学帽 specifically refers to the hat worn during the commute to and from school.
Compound of 通学 (commuting to school) and 帽 (hat).