The son of a former Lawrence school superintendent convicted of embezzlement pleaded guilty in Lawrence Superior Court Tuesday to perjuring himself in grand jury testimony. Wilfredo Laboy II, 38, of Methuen was sentenced to a year of probation, prosecutors said. Last year, his father, Wilfredo Laboy, was convicted of five counts of embezzlement and fraud for misusing the Lawrence school district’s graphic design center to print pamphlets for his son’s pizza shop and ordering school employees to drive his son to work. The elder Laboy was sentenced to two years in a house of correction and three years of probation, said Carrie Kimball Monahan, a spokeswoman for Essex District Attorney Jonathan W. Blodgett. Monahan said that when Laboy was called before the grand jury to testify about his father’s actions, he lied to protect him.