When Mieszko Syski, 8, was barred from Kemp Mill Elementary School last January, he was only one of hundreds of country school children forced to stay home until they had been immunized against measles.

But, while the rest of the affected Montgomery County elementary school pupils got their shots and returned to school, Mieszko has stayed home, while his mother Barbara wages a solitary campaign to do away with the state law requiring school children to be immunized.

The shots, Mrs. Syska believes are still experimental and still potentially dangerous. "Doctors know more and more," the 52-year-old Polish immigrant said last week, "and I believe them less and less."

So Syska - who spells her name with the traditional feminine ending "a," although her son's name ends in "i" - has sued the Montgomery County Board of Education in an attempt to overturn the state law that keeps Mieszko out of school.

This is the first case of its kind in the metropolitan area, although there have been a half-dozen similar cases in other states over the last 10 years, according to Syska's attorney, James Kolb.

If the suit is successful, it could jeopardize Maryland's immunization program, which is considered by U.S. health officials as one of the best in the nation. Officials say that the fewer children who are immunized, the greater chance for measles to spread even among inoculated students.

Despite Syska's urging, the presiding judge in the case has refused to let Mieszko return to the third grade at Kemp Mill until the suit is heard June 22. Meanwhile, Mrs. Syska is tutoring the boy at home.

For two to three hours a day, Mieszko and his mother study multiplication and division, English and Polish. The tutoring is not based on any established curriculum. "If I had known [he would be absent from school] for the full half/year I would have gone to the principal. I thought it was only going to be for a few weeks," Syska said yesterday.

Now she plans to extend the hours of the tutoring. "He won't have exactly what he's be learning in scholl but he's getting just as much from me."

What he does miss, she said, are his classmates."He's very lonely because he needs the companionship of other childred. It's a very unhappy time for him. It will be better when the weather is good and the kids will be playing outside more."

Syska said that she based her dicision not to have her son immunized after reading medical literature."We still don't know what will happen in 20 years," she said.

"It's not preventive medicine when you don't know what the results will be," Syska said.

However, the government maintains that the national program of immunization is necessary, effective, and carries only a minimal chance of side effects, according to Dr. Alan Hinman, director of the immunization division of the Center for Disease Control in Atlanta.

Rash and mild fever can occur in 5 percent to 10 percent of those immunized, and "one time in a million, a child vaccinated in a given month will develop encephalitis," or inflammation of the brain. This rate is half that for children who have not been immunized.

Hinman added that the vaccine, which has been used extensively since 1966, is 95 percent effective for children over 15 months old. "We can say for certain that a child who is not vaccinated has virtually 100 percent chance of getting measles. One in 1,000 of these will get encephalitis, and one in 10,000 will die."

Hinman added that, before the vaccine in 1953, there were 500,000 cases a year of measles around the country. So far this year there are 3,500 reported cases.

Barbara Syska remains unconvinced, and said she plans to keep her child home until she wins her suit. "It is very difficult to explainto Mieszko why he must stay home," she said. "When I told him about the court case, he looked at me and said "Oh, am I a little important person now?"