The board of education in Kasuga, Fukuoka Prefecture, is printing a poster made with portraits of 758 local teachers who have pledged not to do drugs after a public elementary school principal was arrested in May on suspicion of using stimulants.

The poster features small drawings of the teachers' faces with the number 758 in the background. A message in the center says: "I won't do it."

Principal Ikuhiro Matsubara, 57, was arrested in Kochi Prefecture on May 9 on suspicion of using illegal stimulants. After denying the allegation, he later copped to possession and use — charges that led to his indictment and an 18-month prison sentence, suspended for three years, on July 30 by the Kochi District Court.

Naotoshi Yamamoto, chief of the education board, said that given the alarming nature of the case, the board members thought something had to be done to bolster discipline among the teachers. This led to the solidarity poster.

Police nationwide have been stepping up efforts to eradicate "dappo" (loophole) drugs. At least 41 people are suspected to have died from taking the drugs since 2012, the National Police Agency said earlier this month.