A dog on an extendable leash bit and wounded an elementary school student on the Lagunitas School campus last week, spurring Principal Laura Shain to remind West Marin residents that unleashed or unsecured dogs are prohibited on school grounds. The student, who did not provoke the dog, received medical treatment and is doing well, Ms. Shain said. But she noted that the school has had other canine troubles, too. Students have unwittingly and repeatedly stepped in dog excrement left on campus after owners failed to tidy up after their pooches, and dogs have been “running loose and intimidating staff and students,” despite informative signage and direct requests that those with unleashed dogs leave the premises. Ms. Shain wishes to remind everyone that students are often in the fields, gardens and paths between the two schools on the district’s campus and dogs on school grounds must be both leashed and secured, according to both county code and the school handbook.