A girl sporting glasses and a paper Indian headband stares intently at the computer screen. She moves the computer's joystick back and forth tentatively, then looks up at her teacher.

"Get a handle on it. It's like driving a car," instructor Sandy Schrader tells the 4-year-old.

Encouraged, Megan McCuan jogs the stick so that a paddle on the computer screen bats a bouncing ball into a brick wall. Each time the flying white ball hits the wall, a brick disappears with a bang. When a large chunk of the wall is demolished, a pink dragon suddenly emerges and eats several green boxes on the screen.

No, Megan hasn't just won a free game. She's receiving a math lesson.

"How many boxes do we have on this side?" Schrader asks. Megan holds up three fingers. "Three. Right. Now we have to get three on the other side," Schrader explains. Megan punches a space bar three times and produces two matching sets of boxes.

The exercise is typical of the lessons taught through Computertots, a private computer education program increasingly popular at local kindergartens and preschools since it was launched in Howard County in 1989 by Columbia resident Denise Donohue. Part of a national company based in Great Falls, the program shows children still knee-high to a modem how to use personal computers. No dry, by-the-book lessons here. These microcomputer whizzes learn by playing fanciful video games that actually are math and reading lessons.

Tuesday morning at St. John's Episcopal Day School in Ellicott City, Megan and four other youngsters gathered around the Apple computer were so absorbed in their lesson that they temporarily forgot the pre-Thanksgiving vacation fever pervading the school.

Schrader, a teacher at the school and a Computertots instructor, guides the cluster of children through the "Mind Play Math Magic" game. The children take turns encountering the pink dragon and matching the sets of like objects that appear on the screen.

The children's learning experience -- the mood of the lessons -- is just as important as the subject matter, Schrader said.

"It's just so they understand they are in control of the computer and not the other way around. I want them to feel good about the situation," she said.

Manipulating the joystick and punching keys also help develop the children's motor skills, she said.

The real payoff will come years later, when familiarity with keyboarding will be crucial to succeeding in schools, said Donohue, who used computers extensively as an analyst with the Bureau of Labor Statistics.

The lessons "get kids familiar with the computer when it's just a game for them -- fun," she said.

Computertots was started in 1983 by two Great Falls women and grew rapidly. It's now in 17 states. There are eight franchises in Howard County and more than 30 in the Baltimore-Washington area. Computertots competes with at least one similar business in the area, Baltimore-based Futurekids.

Computertots charges $24 a month for four 30-minute lessons. Parents as well as teachers are customers, Donohue said.

Most of her instructors, Donohue said, are former elementary school teachers.