The 13-year-old student who stabbed a fellow student inside a Grulla Middle School classroom this week has been charged with aggravated assault.  The boy was brought before a juvenile judge Thursday and ordered to remain in juvenile custody where he will undergo a psychological workup.  The teen had gotten into an argument with a fellow 8th-grader when he stabbed the boy in the back.  The victim was hospitalized briefly and treated for the wound.  Rio Grande City ISD officials say the suspect has been suspended from school and will likely be expelled.