think on this.

According to the National Center on Time and Learning, a nonprofit research group in Boston, about 170 schools — more than 140 of them charter schools — across the country have extended their calendars in recent years to 190 days or longer. Neither Bethany, who plans to run for student council president, nor Garvin, who was excited about his fourth-grade teacher, seemed bothered by the change. “The kids’ education is more important than all of these breaks that we have,” said their mother, Debra Phillips.

A growing group of education advocates is agitating for more time in schools, arguing that low-income children in particular need more time to catch up as schools face increasing pressure to improve student test scores. “It’s not as simple as ‘Oh, if we just went 12 hours every kid would be Einstein,’ ” said Chris Gabrieli, chairman of the Boston group. “On the other hand, the more time you spend practicing or preparing to do something, the better you get at it.” Education advocates have been calling for more school time at least since the 1983 “Nation at Risk” report presented an apocalyptic vision of American education.

Teachers’ unions, parents who want to preserve summers for family vacations and those who worry that children already come under too much academic stress argue that extended school time is not the answer. Research on longer school days or years also shows mixed results. But studies also show that during the summer break, students — particularly those from low-income families — tend to forget what they learned in the school year. Getting back to school early, supporters of a longer calendar say, is one of the best ways to narrow an achievement gap between rich and poor students.