I got it from the Annual Survey of School System Finances, U.S. Census Bureau, though on checking it again it's between $6,000 and $7,000 (I was recalling from

I got it from the Annual Survey of School System Finances, U.S. Census Bureau, though on checking it again it's between $6,000 and $7,000 (I was recalling from memory). So not what I put in my comment exactly, but doesn't change my main point in any way.