A value-added analysis of student engagement?

The LA Times did something controversial this week: They published a database of the “value added” ratings of thousands of Los Angeles elementary school teachers and hundreds of schools, searchable by name. This is a Big Deal.

I’ve been working my way through the technical paper that describes the study (PDF), but my mind keeps wandering back to a passage from the “Who’s teaching L.A.’s kids?” newspaper article:

On visits to the classrooms of more than 50 elementary school teachers in Los Angeles, Times reporters found that the most effective instructors differed widely in style and personality. Perhaps not surprisingly, they shared a tendency to be strict, maintain high standards and encourage critical thinking. But the surest sign of a teacher’s effectiveness was the engagement of his or her students — something that often was obvious from the expressions on their faces.

I think student engagement is more than just a good indicator of effective teaching. I’m interested to know if there’s any value-added work in which student engagement is the performance measure, rather than standardized test scores. How effective is each teacher at helping his or her students develop a love of learning? And can this intrinsic motivation help a student succeed in subsequent years, even when assigned to less “effective” teachers?