An Arkansas teacher's aide was convicted of assault late Thursday and sentenced to 90 days in jail for encouraging a gang of her fifth graders last month to pummel a boy who was disturbing the class. Pupils said the aide, Amanda Howard of Little Rock, laughed while up to 10 students beat up 11-year-old Eugene Pitts, even -- according to one student -- saying "Everybody kick his butt." The incident came to light after a local hospital that treated Eugene for nose and rib injuries reported it. The school district had never told police. Howard, who was freed on bond, plans to appeal the conviction.