Why Do Teachers Make So Little?

Public School Teacher Salaries: 

http://www.charlotteobserver.com/2012/03/31/418239/nc-government-salary-database.html#.VBLsPPldWSo

Wake Forest Professor Salaries:
http://chronicle.com/article/faculty-salaries-table-2012/131433

Coach's Salaries:
http://www.coacheshotseat.com/SalariesContracts.htm