school-uniform date
A date where both people wear their school uniforms, often associated with teenage romance and a playful, youthful atmosphere.
放課後、制服デートで映画を見に行った。
After school, we went on a school-uniform date to see a movie.
制服デートは青春っぽくて憧れる。
I admire school-uniform dates because they feel so youthful.
Compound of 制服 (school uniform) and デート (date). A modern coinage reflecting youth culture.