Topeka ? Kansas education officials say the achievement gap between rich and poor and minority and non-minority students grew less this year than initially thought.

The state Education Department issued a news release Monday blaming a mistake in calculating results of assessment tests.

The problem arose from how the state dealt with three districts that don’t give their older students the standard state exam. McPherson, Clifton-Clyde and Kansas City, Kan., are using different tests after receiving waivers from the No Child Left Behind education law.

Scores on the alternative exams were converted for use in calculating statewide results. But students from those three districts were counted twice.

The department now says the gap in reading between black and white students grew by 3.1 percentage points, not 7.5 points as initially reported.