What are the implications for parents (in Ohio) who add a teenage son to their auto insurance policy?

I have a 16 year old step son who is anxious to learn how to drive. Before I put him behind the wheel and add him to our policy, I want to gather some facts on how doing so will affect our (my husband & my) clean records. Will his low gpa (grade point average) be a reflection on the policy as a whole? How will any violations he has impact our records and credit ratings? My husband and I are planning on building a house in a year or so and would like to know specifically what kind of risks we are assuming - insurance rating, credit rating and otherwise - so that we don't jeopardize are own hard work because of his negligence! Thanks!