A preliminary hearing for a 25-year-old former teacher in Knoxville who was charged with three counts of sexual exploitation in the past month is set for today. Last month, Justin Mikels, who taught at the district’s GOAL alternative high school and helped coach football and baseball, was charged with sexual exploitation by a school employee, and was suspended pending an investigation on that charge. Mikels was charged with two more counts of sexual exploitation last week of two other female students at GOAL.