A flexible new calendar appears to have achieved the impossible - shortening the academic year for most children while raising standards.
The "intercession calendar" reduces the basic school year from 180 to 170 days but allows schools to offer up to 26 days' extra tuition to children who have fallen behind.
The five rural school districts in Texas that have pioneered the calendar have seen scores in reading, writing and maths tests rise in comparison with other districts using the old "agrarian" calendar which runs from mid-August to May. Disadvantaged children made the biggest gains.
The calendar is divided into six-week segments. If children make good progress for five weeks they can spend the sixh week on "enrichment activities". Many take field trips, technology programmes or reading activities. But they can also use the week for family holidays.
By contrast, struggling pupils come back to school and get intensive, individual attention.
Texas Aamp;M University researcher Jimmy K Byrd says: "The basic premise is that the knowledge gap is minimal each six weeks, and the student in need of assistance does not have to wait until summer school to obtain it."
Just over 650 of America's 15,000 school districts are said to have adopted alternative school years, a 10-fold increase since 1986. But recently some Texan districts reverted to the old calendar.