Republican candidate Mark Kelly, who lost a special election for a seat on the Arlington County Board March 27. (Mark Gail/The Washington Post)

Deep inside Republican Mark Kelly’s campaign contribution list was a curious line, indicating that “Denis J. O’Connell High School” gave $350 on March 15 to the candidate for the Arlington County Board.

Kelly, who lost the March 27 special election to Democrat Libby Garvey, had plenty of other donors who contributed plenty more money.

But, as the blog first pointed out, it is unusual and possibly unprecedented for a school to make a political donation.

Exactly a year earlier, the county board, made up of all Democrats, had rejected a plan to let the school add lights to its athletic fields.

It’s not a violation of state campaign finance law for a private school to give money, and there’s nothing wrong with Kelly accepting it. But it could be a violation of the IRS rules for a school like Bishop O’Connell, which holds a 501(c)3 tax-exempt status, to get involved in political campaigns.

So how did this happen?

Michael J. Donohue, director of communications for the Catholic Diocese of Arlington, said in a statement Monday: “The Diocese learned today that a member of the staff of Bishop O’Connell High School in Arlington County recently used a school check for the sake of convenience to purchase a set of tickets to a political fundraiser for a candidate for local office. This was a significant error in judgment on the part of the school employee as well as a clear violation of diocesan policy. Though all of the $350 in school funds were reimbursed by the employee, Chancery and school officials are presently reviewing the matter, and appropriate disciplinary action will be taken.”