There are miscellaneous items that are part of the school uniform and some of them unlikely at first. Let’s take a look at some of them…
Let’s start off with the bag. Japanese schools generally have a specific bag all students must use. But in cases of manga, book bags can be changed to emphasis the personality of the character. Three types of bags generally used are: regulation (standard) book bag, trendy book bag, or the sporty back pack.
The regulation book bag are black, with a snap in the middle and two straps at each side. The sides are folded but can expand for books and school supplies. Most Japanese students would try to personalise their property, so normally you would see stickers, pins, and whatnot on their book bags. This is against school rules but they do it anyways. :) For bringing out your character, try differing your book bag from unmarked to a jazzed up for a more presonal effect.
You could also take that a step further by giving your character a trendy book bag possibly made by a well-known fashion designer. It can be offset by some sort of design, shape, or even features like a cellphone holder at the side.
I don’t know if they have or do it in Japan but I had a book back similar to the standard book bag when I was young but I had a strap so I could hang it over my shoulder instead of carrying it by the handle on top all the time (quite tedious especially when I was lugging around a bunch of books). You could deign to add a strap to your character’s book bag as well.
The sporty book bag is another “look” most used for the athletic or non-strict character. In America, two popular companies most sought after as a book bag was Eastpak and Jansport. It had one big bag at the back, a small pocket inside of it sometimes, and a smaller pocket up front. The bottoms are thick leather for durability. When making a sports bag, make sure to use some of these features or add more for your liking.
Not usually worn by high schoolers but the elementary students and younger is the cap. The cap is of a yellow color and similar to the “fishing hat” with flapped down lid all around. Young children wear these hats in real life but I’ve seen manga with a completely different design altogether. One such is CLAMP’s Card Captor Sakura with the use of the sailor hat (to go with the sailor uniform ^.^).
In America, schools have a mascot which becomes the schools personal “mark” that identifies them from the other schools. In Japan, I’ve found that private schools generally tend to have their own insignia. A few public schools as far as I noted had their own insignia as well. It is much like the coat of arms of Europe used by the nobility to identify their family. Below are a few that I came across in the net.
As you can see, the school emblem can vary and be presented on the uniform from a patch as in the first image or even as subtle as buttons. The style also varies from traditional looking emblems (with a motto too!), to more modern and fluid looking like the third image from a school called Mura. The emblems can also be found on the school flag as seen below.
School emblems are typically over the right breast if in patch form and usually on the business type uniform. Of course you may change this and be creative like the buttons up above or move the insignia at the side of the arm. I’ve seen manga characters have it on the collar of their uniform, boys and girls, or even on the tie. More dress-down uniforms like the sailor uniform or shirt and pants for the boys tend to not have their school emblem emblazoned on their uniform but you may opt to give your characters that distinction if you like.