Three schools in Baltimore are lengthening the school day based on the "success" of an expanded instruction program in New York ("Three city schools to extend day by three hours," Jan 1).

What success? According to The Sun, New York's overtime students gained 2.2 percentage points in English Language Arts in three years, more than the city average of 1.5 points.

Please do the math. That's a .7 percentage point difference over three years, about one quarter of a percentage point each year.

We can get much bigger gains with a lot less work, with an approach that children will like a lot better than staying in school longer: Invest in libraries and librarians. Studies show that children who do not do well on reading tests often have little access to books, and studies also show that increasing access to books through libraries increases reading as well as reading achievement.

Just reading one extra book for pleasure each year will produce a larger gain in Language Arts than overtime schooling.

Stephen Krashen, Los Angeles

The writer is professor emeritus at the University of Southern California.