My daughter bought a backpack to carry her school stuff to the school. It cost 5292 yen ($44.85 €40.71). These days, it is common for senior high school students in Tokyo to use backpacks as school bags. When I was a senior high school student, I carried a paper bag to the school.
In terms of junior high school, my son uses a hand carry bag. Every student uses the same bag.
Men's socks = 313 yen ($2.65 €2.41)
I bought my socks at Seiyu.