Public schools and police departments are core community institutions. Locally controlled, there are 18,000 police departments and over 13,000 school districts in the U.S. State legislatures and city councils levy taxes to fund these institutions. One is charged to protect and serve; the other to make responsible citizens, prepare the young for the workplace, and gain success in life. Both are crucial to the political, economic and social life of their communities.

Yet well-intentioned reformers ignore obvious similarities and differences between the two. There are, for example, historical similarities. While both tax-supported police departments and public schools began in the early decades of the 19th century and became mired in the political patronage of post-Civil War decades, the early 20th century saw Progressive reformers ending political appointments and pushing for professionalized policing and teaching.

The commonalities end there, however. The model to which police chiefs in those decades aspired to…