Right behind sleeping and going to school, children spend most of their time - about three hours a day - watching television.

And what they see may not be all they get: very young children experience television as a series of disjointed images. Up to age 7, children believe what they are told in commercials as completely as they believe a teacher giving a lesson.Television is a powerful, ongoing influence that helps shape a child's beliefs and behavior - and one that usually comes with no parental control.

A Department of Education study released last month offered worried parents some relief: A review of existing research found no evidence that most children become mesmerized by watching television, that they are reading worse because of it, or that they are spending less time on their school work and getting lower grades because of TV.

Yet some researchers say there's no clear evidence that all those things aren't happening, either.

And there are as many expert opinions about the effects of television on kids as there are experts. Among the points of contention:

-The cause-and-effect link between heavy television viewing and factors such as lower reading ability and school performance. Researchers agree the two are associated, but after that, it's a chicken-and-egg argument.

-Some specialists flatly disagree with the Department of Education findings, maintaining that television-watching does make children more passive and lowers their school achievement.