Wearing school uniforms on weekends

I am curious about why do some young people wear school uniforms on weekends and holidays? I have seen mostly girls, sometimes boys wear a school uniform on a weekend or a holiday. Is it fashionable to wear the uniform even when it's not a school day?

Thank you.

Some schools have classes on Saturdays.

Students often have bukatsu (club sports) on weekends, and wear their uniform or track suits to and from school. Anytime the students go to school they usually wear it, even if they're just going to study.

Also, I live out in the country, and students here often wear their track suit bottoms with a different shirt to walk around during the weekend and go shopping. Weird country fashion.

The most private schools have classes on Sat.

Some school clubs include public/state schools have sporting and cultural activities on Sat, Sun and during school holiday.

Those pupils who attend University/Technical college open day, they often wear school uniform as their formal clothing.

Some girls switch their school uniform to the other girls who attend different school and compare how it looks nice or nasty(almost all girls, boys don't do this).

Some girls simply don't have much private clothing. Those girls wear school uniform as they go out with friends.

Various reasons exist.

Interesting to know. We noticed quite a few girls in school uniform when when we were at Disneyland on a weekday in mid-September, and couldn't quite work out what was going on. There didn't seem to be loads of them wearing the same and sticking together like it was a class trip, but were thinking if it was a day off school or they were skipping class then why would they be wearing it? In the UK they'd be ditching it ASAP both for fashion reasons and to avoid being asked why they're not at school!

School trips are often held over both weekdays and weekends, and students are usually supposed to wear their uniforms. Trips to Tokyo area almost always include Tokyo Disneyland.

Tokyo Disney Land and Sea officially don't permit to enter those who wear school uniform.
Those people who wear school uniform are either school trip pupils(there pupils are permitted by TDL) and matured people who are already graduated high school but still want to wear school uniform in TDL.
It sounds strange but there are still many school graduate who want to wear their school uniform and visit TDL with their school friends sharing good memory and keeping the friendship.

Ha! That reminds me of my son's graduation day. A classmate of his was saying, "Hey girls, you've got only a couple of hours left. If you wear that uniform tomorrow, you'll be doing cosplay!"

That much-repeated rumor about school uniforms "officially" being prohibited at TDL is just another urban myth like the one about kids being kidnapped for organ harvesting. Anyone who's actually been there will know that there's no problem with schoolkids (or adults) wearing uniforms.