Blame the Teachers?

From Changing the Odds for Student Success: What Matters Most, Mid-continent Research for Education and Learning(McRel}, by Brian Goodwin, 2010.

“When it comes to student learning, research points to the tremendous influence of a handful of variables as the root causes of their successes or struggles. MCREL research conducted by Robert Marzano in 2000, published as A New Era of School Reform: Going Where the Research Takes Us, analyzed multiple influences on student achievement and found that 80 percent of the variation in student achievement can be attributed to four student­-level variables:
“1. Home environment 2. Prior knowledge 3. Aptitude 4. Interest and motivation
“That leaves just 20 percent of the variance in student success related to teachers (13%) and schools (7%).