I have heard something I have had a little trouble confirming on this subject. That it is against school regulations for high school students to have part time jobs.
That's the first that I've heard of it. Mandatory (or "guaranteed") education only includes elementary and junior high school. Although most students also end up going to high school, I believe it is not technically mandatory, so it would only seem appropriate that part time jobs are available to high-school-aged teenagers (although what types of jobs they can qualify for, with only junior high education, is anyone's guess).
More likely such "no work" policies are probably different from one high school to the next, with no single accepted standard.
A quick search for 高校生 バイト (high school student, part time job) yields lots of job listings and application information.
This page of general information suggests some jobs available to high school students, such as cash register, waitressing, moving companies, and distributing flyers.
Why is it that only girls get stigmatized for sex working? I hate the double standard. :<
Worry not,
shotacon is alive and well in Japan, too.