Comprising the bulk of the top 10 list are small liberal arts schools like Sarah Lawrence College in New York, Kenyon College in Ohio and Bennington College in Vermont--all high on prestige and low on student-teacher ratios.

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To be eligible, states also had to adopt "college- and career-ready" achievement standards and must link teacher evaluations to student achievement.

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Harvard and Columbia researchers found a good fourth-grade teacher makes a student 1.25% more likely to go to college and earn a higher salary.

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