According to newspaper reports last week, Durand Academy in south London has spent £200,000 on PLMR and libel lawyers Carter Ruck.
The school is embroiled in a legal fight with Lambeth Council.
PLMR boss Kevin Craig joined the school's board of governors in 2010 - a year after his agency was appointed by the school. PLMR was reappointed to the £110,000 account last month.
Craig told PRWeek: 'We're really proud of our work for Durand. Our work has been predominantly positive PR.'