By Dr. Marciene Mattleman

PHILADELPHIA (CBS) – Year-round schools are not new and lately there’s been a surge.

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Currently year-round calendars account for 4.1% of public schools and 11% are charters. Most have been attempts to solve overcrowding. Recently there have been grant programs in Virginia and Michigan for implementation.

In year-round schools, kids attend the same number of days as those in traditional schools, have two or three mini-vacations and, by not having the long summer off, can avoid summer learning loss. No longer do they use the 100-year-old model.

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US Senator Mark Kirk of Illinois has introduced legislation that will promote year-round pilots in underperforming schools mostly serving low-income families.

A 2011 study at Simpson College in Iowa showed statistically significant results in improving achievement scores; but most studies found little differences – some only modestly positive.

Testimony from principals has been encouraging; but parents don’t like family schedule disruption.

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Learn more in Education Week.