An exterminator found a rotting corpse wedged in the chimney of a Queens public school Tuesday morning after he was called to investigate a putrid odor, cops and sources said. The pest control worker made the grisly discovery just before 9 a.m. when a janitor dispatched him to P.S./I.S. 113 Anthony J. Pranzo at 87 Street and 78 Avenue in Glendale to investigate the stench, according to authorities and law enforcement sources.