Prefectures have no set rules for expelled public high school students to appeal their schools' decisions, a survey of education boards in all 47 prefectures showed Thursday.

In addition, only Hiroshima Prefecture has set explicit rules on expelling students, and most have left the decision up to school principals, according to the survey conducted by Kyodo News.

Some boards may act as a mediator between such students and their schools. But students have no recourse except to file time-consuming lawsuits.

"We have spent enough time hearing opinions from students and their families," the Nara Prefecture board of education said in its reply to the survey, explaining why it finds an appeals process unnecessary.