As Nancy Reagan begins her second year as first lady she is trying to shift attention away from criticism about her extravagant clothes and social life and toward certain social problems to which she has pledged her support.

Yesterday, she flew here to look in on a project that combats drug abuse among youth and relies heavily on parental participation.

"I'm a big believer in the family," Mrs. Reagan told 20 children, aged 9 to 12, and their parents in one of Florida's six school-based pilot prevention programs called "Alpha." The approach is to change behavioral habits that can make the youngsters vulnerable to drugs, alcohol and poor mental attitudes.

Sitting in a classroom with the children, their parents and their teachers, the first lady heard personal testimony about the success of the program so far. One teacher asked the kids how they might react if someone let the air out of their bicycle tires and there were two possible culprits -- before and after being involved in the program. "I would have cremated both of them," said one girl of her "before" attitude. But after Alpha, their reactions were more thoughtful: "I would have gone to the principal," or "I would have gone for help."

"I still would have beat him up," said one boy.

The parents told Mrs. Reagan about how the program helped them to deal with the stress of rasing children today. One mother said, "It helped show me I was being too soft . . . he needed the individual attention that is impossible to get in a classroom anymore."

Harvey Landress of the sponsoring group, Operation Par, said, "We help parents recognize that they do have control over their children's behavior." Among the early signs of problems that they look for, according to Landress, are how disruptive a child might be in the classroom, whether he is withdrawn or has difficulty with academics or his peers. Cofunded by the state and county, Alpha costs about $2,000 a pupil. There is no federal money involved.

White House aides cite the privately funded program, which is largely for middle-class children, as an example of people solving problems locally without government help.

Mrs. Reagan, who seemed relaxed in the encounter session, wore a beige Adolfo dress and jacket and was serenaded by the Pinellas Park schoolchildren to the tune of "Hello Dolly." She told the Alpha group it was important "learning self-worth and being aware of yourself as a person and what you can do regardless of the peer pressure."

To the parents, she said, "Being a parent is probably the most important thing we're given to do in our whole lives and the one we have no training for at all ."

This is Mrs. Reagan's first outing this year to draw attention to drug prevention and rehabilitation programs around the country. Today she flies to Texas to meet with another rehabilitation groups.