Children who attend high-quality preschool classes do better for a time in language and math than those who attend lower-quality classes, according to the latest "Cost, Quality and Child Outcomes in Child Care" study. The conclusions are similar to the researchers' first report, in 1995.

There was evidence, however, that the differences in performances between the two groups narrowed by the second grade.

• By the second grade, the report said, "the difference between the language skills of children in high- and low- quality care decreased." (See figure)

• This occurred because "the children have had a number of experiences in kindergarten and the first and second grades," picking up knowledge along the way.

• Children from higher-quality preschools continued to do better in math.

• Children whose mothers had lower levels of education "are affected more by the quality of child-care experiences than other children." (See figure)

Critics say the study overlooks the fact that children need and parents want more time with one another.

The report will no doubt play a role in the emerging battle over mandatory, taxpayer-funded "universal preschool" for all 3- and 4-year-olds.

Darcy Olsen of the Cato Institute says that requiring preschool classes is misguided because early intervention programs -- including Head Start -- have been shown to have "no meaningful long-term effects on the cognitive, social or emotional development of participating children."

She adds that it is "irresponsible to expand public schools when so many are failing to educate the children already enrolled."

Sources: Cheryl Wetzstein, "Study Highlights Child Care Benefits, Backs Calls for More Federal Funding," Washington Times; and Irvin Molotsky, "Study Shows Importance of Preschool and Child- Care Quality in Education," New York Times; both June 9, 1999.