AUSTIN — Gov. Rick Perry urged lawmakers to cut school property tax rates by an additional $2.5 billion Wednesday, and House Speaker Tom Craddick said his chamber is already on track to consider the idea. But Lt. Gov. David Dewhurst, who presides over the Senate, said the state can't afford it unless revenues dramatically increase, not if lawmakers want to balance the budget and meet their commitment in future years to subsidize already-promised tax relief.