In Taiwan, from elementary school to high school, students carry (soft) canvas 帆布書包 with one shoulder strap slung diagonally across. But just now I checked, it seems that most carry a backpack.

Now that in Japan, randoseru is used by students in elementary schools only, what do students of middle and high schools carry (as well as wear)?

Japanese-English dictionary:
* kaban かばん 《鞄》 (n): "bag; satchel; briefcase"
* uwabaki 上履き 【うわばき】 (n): "hallway slippers; indoor shoes"  (The uwa- is one of many Japanese pronunciations of kanji 上. The verb 履く(pronounced ha-ku) means :to put on (lower-body clothing, e.g. pants, skirt, footwear)" and 履き (pronounced ha-ki) is the corresponding noun. Because haki is not in the starting position of a compound word, it is softened here to baki.)
   ^ Its antonym is 下履き(pronounced shitabaki) meaning "outdoor shoes."
* tsume-eri 詰襟 【つめえり】 (n): "stand-up collar"
   ^ tsumeru 詰める 【つめる】 (v): "to cram"
* hotena はてな; ハテナ (int[erjection]): "(1) dear me!; good gracious!; (int) (2) (used before sentences expressing a doubt) well; let me see; now"


(1) secondary education in Japan  
https://en.wikipedia.org/wiki/Secondary_education_in_Japan
("Secondary education in Japan is split into junior high schools (中学校 chūgakkō), which cover the seventh through ninth grade, and senior high schools (高等学校 kōtōgakkō, abbreviated to 高校 kōkō), which mostly cover grades ten through twelve."
, whose photo in the upper right corner carries a caption: "Japanese high school students wearing the sailor fuku."

The fuku is Chinese pronunciation for kanji 服.


(2) school uniforms in Japan
https://en.wikipedia.org/wiki/School_uniforms_in_Japan

section 2 Usage: "The Japanese junior and senior-high-school uniform traditionally consists of a military-styled uniform for boys and a sailor outfit for girls." On the left margin is a photo whose caption says in part: "At some schools, students wear uwabaki [defined at the top], a kind of soft slipper meant to be used only indoors. * * * Regardless of what type of uniform any particular school assigns its students, all schools have a summer version of the uniform (usually consisting of just a white dress shirt and the [same] uniform slacks for boys and a reduced-weight traditional uniform or blouse and tartan skirt with tie for girls) * * * "

section 3 Gakuran: The gakuran (学ラン), also called the tsume-eri (詰襟), is the uniform for many middle-school and high-school boys in Japan. The colour is normally black, but some schools use navy blue.   The top has a standing collar

section 4 Sailor fuku: "It was introduced as a school uniform in 1920 at Heian Jogakuin (平安女学院)[not high school- but college-level; founded by Church of England 英国国教会 and based in Kyoto] and 1921 by the principal of Fukuoka Jo Gakuin University (福岡女学院),[10] Elizabeth Lee. It was modeled after the uniform used by the British Royal Navy at the time, which Lee had experienced as an exchange student in the United Kingdom.

Note for section 3 above:
(a) The ja.wikipedia.org for 学生服 states: "学ランの「ラン」は和蘭陀の「ラン」を指し、江戸時代に洋服を蘭服と呼んでいたことに由来するという説がある。つまり呉服（中国由来のスタイルの服＝今でいう和服）に対しての蘭服（西洋の服）として、蘭学同様鎖国中は和蘭陀が西洋全てを代表する名前となっていたためである[2]。"

my rough translation: The ran in gakuran refers to the ran in Oranda 和蘭陀 [Holland]. Edo period called 洋服 as 蘭服. in contrast to 呉服 (from China, which is nowadays we call 和服), the 蘭服 to reference 西洋の服 is same as 蘭学, as during 鎖国, 和蘭陀 [Holland] stood for the whole 西洋.

The 呉 in 呉服 refers to the state of that name dyring 中国の春秋時代, not the one of three-kingdom period.   
(b) collar (clothing)
https://en.wikipedia.org/wiki/Collar_(clothing)

section 4 Types:
• Standing or stand-up [in Japan: 詰襟, defined at the top]
• Turnover [in Japan: 折襟 (pronunciation: ori-eri); the collar we see everyday everywhere]
• Flat
(i) For stand-up collar, see Pattern Construction for Stand-up Collar. M Müller & Sohn (Munich-based; The founder was German, Michael Müller), Mar 6, 2023.
https://www.muellerundsohn.com/e ... or-stand-up-collar/
(ii) More examples of collars can be found in
Collars. Family & Consumer Sciences Extension, School of Human Environmental Sciences, College of Agriculture, University of Kentucky, undated (document No: CT-LMH.185).
https://fcs-hes.ca.uky.edu/sites ... iles/ct-lmh.185.pdf


(3) In Japan, both 中学生 and 高校生 (the latter in Japan means high school student; male and female alike n both) carry not (rigid) randoseru but (soft) kaban with two shoulder straps. See
(a) Inside the Bags of Senior High School Students. In Lesson 18 Comparing - 100-yen Shop. Japan Foundation 国際交流基金 (1972- ; independent institution of Japan government based in Tokyo to disseminate Japanese culture), undated
https://www.erin.jpf.go.jp/en/lesson/18/let-us-see/

Viewing the video or not is not important; what you should do is view photos 1 (which is leftmost) and 2 in the top row and read respective captions.