THIRTEEN-year-old Cedric Dixon worries about his mother. Knowing that his grandmother suffers from hypertension, he told his mother they shouldn't salt their food any more.

"I know I'm not really supposed to have as much salt as I eat," says Margaret Dixon. And she has cut down. She's lost 10 pounds since Cedric first learned in school about the hazards of high sodium consumption. She doesn't add salt to her food any more. She bakes chicken with garlic powder now and refrains from using such high-sodium foods as hot dogs, pickles and canned meats.

Cedric and 59 of his Baltimore City Public School classmates were part of an apparently successful experiment established under the auspices of Johns Hopkins School of Hygiene Public Health by Dr. Ruth McKay and co-worker Dr. Roberta Hollander.

The experiment, conducted at Elmer A. Henderson School, is only "apparently" successful because scientists aren't satisfied until an experiment has been duplicated -- something they hope to do next week -- and long-range results are measured.

Until then, they have to be content with the preliminary results. In this case, that means the students consumed 33 percent fewer high-sodium snacks by the end of the study. It means that 47 percent of the parents -- Margaret Dixon among them -- changed their dietary habits to include less sodium.

How do you do it? How do you get 12-year-olds to cut down on salt when it shows up in the snacks and fast foods they commonly eat?

With a little insight, according to investigator McCay, some common sense, "and a whole lot of community support."

Baltimore joined the effort full force. Johns Hopkins, city school officials, local health clinics, snack food companies, retailers -- every part of society that touched those students -- became involved in the week-long sodium-education effort. Research shows, says Dr. McKay, that life style changes come easier when all phases of one's life support them.

McKay invented a board game called "Hold the Salt" and developed a health curriculum around it. To win the game, a player must move his board marker around a board divided into quarters (breakfast, lunch, dinner and snack), acquiring the fewest number of sodium points.

The spaces dictate which food the player chooses for that meal. If he lands on a "high-sodium" main dish for breakfast, he picks from the high-sodium stack of cards and he could get bacon, or he could get ready-to-eat breakfast cereal. Funny, breakfast cereal doesn't taste salty.

It's all part of the game. High-sodium foods don't always taste salty, but they come with high points nonetheless. Players tally their points -- high ones for canned soup and pickles because they have lots of sodium, low ones for fresh fruit and unsalted snack foods -- and the first player with the fewest sodium points wins. The goal is to get not more than 2,000 milligrams of sodium (the sodium contained in one teaspoon of salt).

The education project uses the game as a pivot. There's a lot more involved. Teacher Mattie Blackwell says she appreciated the sodium lessons because "a lot of the activities were 'hands on' activities that the children enjoyed doing, and they got treats."

The treats were unsalted snacks, like the unsalted potato chips donated by Herr's in individual snack-sized bags. While teachers Blackwell and Louise Westry taught how sodium can hurt you, about high blood pressure, strokes and heart disease, the children got to munch on appropriate snack foods.

To reinforce the lessons taught in class and by the game, the children were given low-sodium choices in the lunch line. Lunchroom manager Luberta Jones says it took her about an hour to make cards which would identify how many sodium units -- corresponding with those in the "Hold the Salt" game -- were in each of the foods offered in the lunch line. While students opted for the high-sodium chocolate cake over fruit salad, they chose baked chicken over the usual favorite, pizza.

Low-sodium messages were sent home to parents, clipped to more snack-sized packages of unsalted potato chips. Researchers capitalized on the opportunity provided by the sixth-grade modern-dance recital -- parents received a nutrition lesson between two parts of the show. "High blood pressure is a problem in the community, so it's relevant to the parents," says McKay.

McKay and her research director, Dr. David Levine, insist that parents want to become involved in preventative health. "Good health care should involve the family of the person with the chronic condition," says Levine. " Parents welcome being included as long as you give them specifics on what they can do. All that's needed is a physician or nurse to involve the parent, or spouse."

In two public health clinics frequented most by the families involved, posters and reading material reinforced what the children had learned in school.

This particular group of school children -- and parents -- was chosen for the study because they are at "increased risk of having hypertension high blood pressure ," says Levine.

First, they are predominantly black and have a high incidence of hypertension in their families. Blacks, for reasons not entirely known, are 10 times more likely to die of stroke and other complications of hypertension than whites. In a statewide survey, 19 percent of the white adults in Maryland were found to have high blood pressure, compared to 23 percent of the black adults.

Second, they might be more inclined to have high-sodium diets. Another survey showed that 9 percent of white children in poor families ate a salty snack once a day, as compared to 27 percent of the black children.

Third, they come from urban backgrounds and are therefore predisposed -- for reasons of stress or otherwise -- to suffer high blood pressure.

Researchers will go another round of experimenting before Baltimore schools health-education coordinator Betsy Simon considers putting the sodium lessons into the system's curriculum. The new experiment will call less for the work of Hopkins researchers, relying more on the teachers themselves. If it's deemed a success, researchers will develop "booster" lessons to reinforce the primary knowledge in older students.

McKay focuses on this age group because "children between 6 and 18 years are eating much more sodium in the diet than they ever will again," no matter what their race, no matter what their sex. Some researchers believe that this heavy consumption early in life may contribute to sodium sensitivity later on. If they learn to make good choices early, they'll develop sound dietary habits.

Also, the prevalence of "juvenile hypertensives" -- children with high blood pressure -- continues upward. In the old days, no one looked for hypertension in the young, so nobody knows how frequently it occurred. Doctors test children these days, and find hypertension among them.

How many children suffer high blood pressure? "Lots." says Dr. Levine. "Probably in the millions. High blood pressure is something that does not start in adulthood." Doctors want to avoid treating a child with medication for a disease that may last his entire life. No one knows what such treatment means in terms of long-range health.

So early education becomes a most important and, the researchers hope, most effective tool. Perhaps it will be as easy as child's play.