Mark Bernstein, a former NY State superintendent of schools, considers how school culture inhibits substantive teacher and administrator evaluations:

School culture strongly frowns upon administrators rating teachers as less than satisfactory. Most elementary schools have fewer than three- or four-dozen teachers; they constitute a family with members supporting one another regardless of deficiencies. Fellow teachers are well aware when colleagues have personal issues that might diminish their effectiveness, and they expect administrators to compensate by being generous in their evaluations. 

Administrators who are critical of teachers often lose the respect and cooperation of the faculty. Moreover, how can administrators explain to parents that their children have teachers rated ineffective but who remain in the classroom? Administrators in New York—other than school superintendents—are also eligible to receive lifelong tenure. Many of them thus have little incentive to rock the boat.