getting part time job with a dependent visa

Hello, I’m currently a HS student wanting to work a part time job here in Japan, I know I have to get a permit to work in Japan in the immigration office, but last time I went there I brought my alien card, ID, and passport. They told me I needed a 許可書 from school. When I asked my school about it, they don’t have one. They tell me that there were alot of foreigners in my school and have never even asked for that. They even called the immigration office if it was needed for high school students and they said no, they don’t. I’m taking a day off and going to the immigration office tommorrow. I also have read online that you dont need that. Do I really need the Kyoka sho or no? Also, last time they gave me a form and does my school have to write the bottom part? The Agent or Authorized Person part?http://www.moj.go.jp/content/000099659.pdf Please, help me. Thanks in advance.

generally speaking, high school students in Japan are minors.
since you are on a dependent visa, your parent(s) are in Japan. I think it is better to go to immigration office with your parent(s). if they request some document of permission. your parent(s) can write it.

Some (many?) schools forbid students from having part-time jobs (welcome to Japan!); maybe your prospective employer wants to make sure your school is not one of them?