TORONTO - Homework is of little benefit to students from junior kindergarten to Grade 6, say the authors of a just-released Canadian study, who also found it is often the source of stress and burnout in children, as well as conflict -- even marital stress -- for many families.

The study by two Toronto professors found homework rates vary wildly from student to student, and from grade to grade, with some Grade 2 students spending less than 10 minutes a night, while others log more than 45 minutes.

On average, Ontario students spend almost 40 minutes on homework a night, compared with 32.6 minutes in other provinces.

The authors say this finding is statistically significant.

While research shows some benefits to homework in Grades 7 and 8 and high school, there's scant evidence it improves student achievement in the younger years, say professors Linda Cameron and Lee Bartel of the Ontario Institute for Studies in Education at the University of Toronto.

"For elementary school, especially for the primary grades, I am down on homework entirely," said Cameron, a former kindergarten teacher.

Studies have shown reading with, or to, children every day is the only conclusive way to boost their academic success, and Cameron believes that should be the only "homework" for younger children.

There is a growing body of research in the U.S. that has found homework isn't all it's cracked up to be.

Some American elementary schools have cut back or entirely banned homework.

Cameron and Bartel embarked on this study because of the lack of comparative Canadian data.

In their study, more than 1,000 parents were surveyed and said while they like the good work habits homework promotes, as well as how it helps parents be involved in their children's academic lives, the amount students are getting is interfering with family time, causing stress and even marital troubles.

"Kids are at school for six and a half hours ... and some are on buses at 7:30 in the morning and get home from school at 4:30 or 5 o'clock. That's a very long day, and then they are supposed to do homework?" Bartel said.

"What do we expect of unionized workers, with hours and breaks, and what do we expect of our children? Schooling is their work."

Generally, students should spend 10 minutes per night per grade on homework. Toronto public school board guidelines recommend 10 to 30 minutes for junior kindergarten to Grade 3; 30 to 60 minutes from grades 4 to 6; 45 to 90 from grades 7 to 9; and up to 120 minutes for older high school students.