WASHINGTON — Should preschool be more about ABCs or learning to play with others? With the help of Twiggle the Turtle, scientists found out that youngsters do better if they do both.

So concludes a major study in Head Start programs in Pennsylvania, research with implications for preschools and parents everywhere.

Face it, 4-year-olds are lovable but self-centered, impulsive and prone to meltdowns. Teaching them not to whack a classmate who snatches a toy is a big part of preschool socialization.

But growing awareness that early learning is important to future school achievement has put more pressure on preschool's academic side, especially efforts to eliminate achievement gaps between low-income and wealthier students.

Both skills are intertwined, said Penn State University psychology professor Karen Bierman, who led the new study.

"If preschools focus just on the facts — let's just get the letter knowledge in, let's just get the number knowledge in — they're really missing the engine that's going to drive the desire and motivation for learning," she said.

To prove the relationship, Penn State researchers turned to Head Start, the federal preschool program for poor children.

With funding from the National Institutes of Health and other federal agencies, they divided 44 Head Start classrooms with about 350 4-year-olds. Half taught a traditional Head Start curriculum.

The other half added to their traditional teaching a program called REDI Head Start that included weekly special social lessons — puppets or stories that teach specific problem-solving skills.

Take Twiggle the Turtle. He pushed his friend after she knocked over his block tower, and thus couldn't play anymore. A wise old turtle told Twiggle that when he got upset, he should go inside his shell, take a deep calming breath, and say what bothered him and how it makes him feel: "It really made me mad that you knocked my blocks over."

Cross your arms to be like Twiggle in his shell, the teachers tell their preschoolers. Then practice what James might say if Suzie takes the toy he wants, or if Billy says something mean to Tommy.

Instead of the vague "use your words" advice that parents tend to spout, "be like Twiggle" became the theme and a good habit.

"What's really beautiful: You'll see children over in the blocks center and someone stands up and does the turtle and talks, and someone else does the turtle and talks, and then they sit down and play again," Bierman said.

Another enrichment tested: More intense reading-readiness instruction. It included interactive reading — where the teacher asks questions after each page or so to work on vocabulary and comprehension — and listening games to tease out discrete sounds in words. Both require self-control to focus.

By year's end, preschoolers given enriched instruction scored higher on tests of school readiness, both social and academic, Bierman reported Friday in the journal Child Development.

Some examples: Seventy percent of kids in the enriched classes showed little or no disruptive behavior, compared with 56 percent in the regular classes. Twelve percent of the enriched students still struggled to focus attention on academic tasks, compared with 21 percent in regular classes. And 20 percent in enriched classes exceeded a national vocabulary norm compared with 15 percent in regular classes.

Preschools always aim to teach good behavior, but a crowd-control approach — "stop doing that, put that down, don't pull his hair" — doesn't help children learn to resolve conflict, said James Griffin of the NIH's National Institute of Child Health and Human Development.

The new study shows how to teach children positive steps, not just what to avoid, in a way that's easy for busy teachers, he said. Much of the enriched curriculum is commercially available, along with similar programs also being studied in Head Start.

"You can impact both social, emotional and the pre-academic skills at the same time, in the same classroom, with the same teacher, without overwhelming the teacher," Griffin said.

Bierman next wants to train parents to reinforce these lessons.