SAN FRANCISCO, Aug. 21 - Edward Vazquez Jr., 6, has numerous educational tools at his disposal. He learns math from flashcards and the alphabet from a popular electronic gadget called the LeapPad. But when it comes to instruction, the family's personal computer sits dormant.

"He has a lot of toys for learning -- not the computer," said his father, Edward Vazquez, 28, a waiter in San Francisco. One reason, Mr. Vazquez said, is "you don't see a lot of that software."

That statement would have been unthinkable a few years ago. In 2000, sales of educational software for home computers reached $498 million, and it was conventional wisdom among investors and educators that learning programs for PC's would be a booming growth market.

Yet in less than five years, that entire market has come undone. By 2004, sales of educational software -- a category that includes programs teaching math, reading and other subjects as well as reference works like encyclopedias -- had plummeted to $152 million, according to the NPD Group, a market research concern.