Ask at the actual school if they have any suggestions or who they recommend as far as a driving school. In many cases the school will actually endorse certain driving schools over others. They have seen more kids than anyone else so they will know what they are talking about.
One huge consideration when it comes to driving school is the cost. You should comparison shop in regards to price for the class. See if they offer any type of discount for referrals or if they are a second family member to attend the same school. Always ask if they offer discounts of any sort as well.