Mauricio Mendoza, who worked at Hartman Middle School, was arrested Wednesday on the charges and posted $50,000 bond.
He had been fired from HISD since December, when HISD police launched an investigation after school officials received a report of the allegations. At that time, HISD also contacted Child Protective Services.
HISD would not reveal how Mendoza was employed at the middle school except to say he wasn't a teacher or tutor. HISD also wouldn't comment on what the allegations were, who reported them, what the relationship was between the child and Mendoza, or whether the child was male or female. In its press release, HISD described the alleged aggravated sexual assault as "inappropriate contact" with the student.