Children's scores in school achievement tests fall off in close relation to the amount of time they watch television each day, according to the California Department of Education. It unveiled the results of a survey of more than half a million public school pupils in which their scores in the state's 6th and 12th grade assesessment tests were measured against their TV habits. "I was not surprised that TV had the effect of decreasing their test scores, but I was surprised at how much," said Alexander I. Law, chief of the department's office of program evaluation and research. "There is a very substantial relationship."

Law insisted the survey was not a scientific experiment, but an effort to gather information. "It's a question of association, something like smoking and lung cancer," he said, predicting that the California survey would set off widespread research into the effect of TV on students. The survey indicated that sixth graders who watched TV an hour or less a day achieved scores about 7 percent higher than those who spent four hours or more daily in front of the tube. Test scores declined rapidly for all children who viewed television more than three hours a day. For high school seniors, the scores fell almost in direct relation to the amount of time they devoted to television. Twelfth graders watching TV six hours a day or more got scores about 14 percent lower in all areas than those who confined their viewing to an hour or less. The survey embraced 281,907 sixth graders tested in May and 233,125 high school seniors tested in December 1979 under California's school assessment program. Third graders also were tested but did not figure in the television survey. The tests, less than an hour in length, cover reading, written expression and mathematics. The only group of TV watchers whose test scores showed slight improvement were sixth grade children from lower income families where parents had little education. Law said that for these children, exposure to up to three hours a day of television apparently improved their language skills. Law said it was the first mass effort to measure the effect of TV on children's school achievement. He said the results were about the same as those of tests made elsewhere with children in classroom size groups. Law said the children tested estimated their daily TV watching time themselves. The were asked to exclude time spent viewing sports events.

"I think their estimates were conservative," he said. "We all watch TV more than we think we do. "TV watching is something we in the schools have no control over. All we can do is hold up the results and show what's happening."