Rosemary, a High-School Principal, Argues That So-Called Effective Schools Are

Rosemary, a high-school principal, argues that so-called effective schools are difficult to achieve. She uses the following reasons to support her argument. Which is least defensible?

A) There is little agreement on a definition of school effectiveness.
B) No two schools have exactly the same improvement needs.
C) There are few examples of successful school effectiveness projects that can provide lessons for others.
D) Schools are complex organizations that are difficult to change.