Hi Timothy,
Education Trust has done a lot of research on teacher effectiveness -- see this slideshow for some data:
http://www.edtrust.org/dc/presentation/teacher-and-principal-effectiveness-what-do-we-know
Another interesting study on closing the achievement gap is here:
http://www.economics.harvard.edu/faculty/fryer/files/hcz%204.15.2009.pdf
This and other studies indicate that that these challenges are surmountable. Many schools, like the school in the movie, are closing the achievement gap, showing that regardless of socio-economic status, their students can achieve at the same levels as students in wealthier suburbs.