NASHVILLE (AP) — A bill to assign letter grades to public schools in Tennessee is headed to Gov. Bill Haslam's desk.

Supporters say the current system of rating schools on a scale of one to five can confuse parents who may not know that the lower numbers are worse scores. Under the bill sponsored by Rep. Glen Casada of Franklin and fellow Republican Sen. Dolores Gresham of Somerville, schools would receive grades A through F.

The Senate voted 30-0 to agree with a House provision that would have the executive branch to develop the grading system. The Senate bill had originally assigned that task to the State Board of Education.