A bat found on the grounds of a school in Mercer County on Tuesday has tested positive for rabies, officials said. Recreational staffers found a brown bat that was alive and moving near the playground at Community Park Elementary School in Princeton around 9 a.m., the township said in a news release. Princeton Animal Control took the animal and submitted it for testing. On Wednesday, they received confirmation it had tested positive for rabies, the township said. As of Wednesday night, there were no known human exposures to the rabid mammal. Rabies is a fatal virus that affects humans when the…