Student Achievement in Edison schools has been heading steadily upward as reported in the Fifth Annual Report on School Performance:

Comparing the gain rates of Edison schools to over
    1,100 schools with similar levels of economic
    disadvantage and ethnicity shows Edison schools
    out-gaining comparable schools by two or three
    points per year.
Edison schools have, from 1995 to 2002, increased
    the percentage of students achieving standards by
    an average of 4.0 percentage points every year.
Edison schools have, from 1995 to 2002, increased
    the national percentile rank of its students by an
    average of 4.4 percentile points every year.
From 1995 to 2002, Edison schools reduced the
    failure rate on criterion-referenced test by an
    average of 3.6 percentage points every year.
The average annual gain rates of Edison schools
    with predominantly African-American students
    (90 percent or higher) are 4.7 percentage points on
    criterion-referenced tests and 4.4 percentiles on
    norm referenced tests, respectively.
Edison has been asked to work in a number of
    No Child Left Behind “needs improvement”
    schools. Under Edison, these schools have
    posted average annual gain rates of 5.8
    percentage points and 4.3 percentiles on
    criterion-and norm-referenced test, respectively—
    several times state and local norms.
Eighty-four percent of Edison schools are
    achieving at higher levels now than when they
    opened or became Edison Schools.
On average, 85 percent of Edison parents rate
    their school an A or B, with A being the most
    popular grade.

The complete Fifth Annual Report on School Performance is available here in Adobe Acrobat format in three parts:

Part 1: Front Text
Part 2: School Reports
Part 3: Appendices

Please note that file downloading time will vary depending on the speed of your Internet connection.