Melvin Waters Jr., an outspoken 14-year-old from Forest Heights, understood the tough Prince George's policy mandating expulsion for possession of weapons or drugs in school. He thought it was only for troublemakers--like the youths who threatened to beat him up over a scuffed shoe just before Christmas.

So when he sneaked a homemade nunchaku--two nine-inch lengths of shovel handle connected by a four-inch-long chain--into his gym bag Jan. 4 because he heard he was going to be jumped, he figured he would not be punished for defending himself.

"It's right; it [the policy] should be there because kids will end up bringing guns and everything up there," said Waters, who also answers to "Bubbles" and "Rock." "The policy is right, but I never thought it would happen to me."

But Waters' principal at John Hanson Junior High School has recommended his expulsion, stemming from an adolescent showdown on the sidewalk in front of the school between Waters and six other students.

Waters' parents said Principal John Flynn told them that none of the attackers were suspended after the incident. Flynn said the students were punished but refused to elaborate.

Meanwhile, Melvin, an average student whose parents hold master's degrees, is likely to be expelled because the school board law allows little flexibility.

The operative part of that rule reads simply, "The Board of Education expresses the strongest belief that any student properly found with the possession or use of weapons be expelled by the superintendent of schools."

More than 60 secondary students have been expelled this year under the policy passed by the school board last August, compared with only one expulsion last year.

Students from "good" homes with no serious discipline problems have been expelled as have habitual troublemakers, according to school officials, a result that has drawn some criticism from several school board members.

School officials expected the number of expulsions to decline after students realized the policy would be enforced, but expulsions are continuing at about 15 a month.

The majority of the board still supports the new rules, however.

"Only time will tell, but at the moment the board is very pleased with the policy," said Brian J. Porter, a school spokesman, who otherwise declined to comment on the Waters case, except to note that his punishment, even in self-defense, has nothing to do with discipline meted out to his antagonists.

Waters said he learned to defend himself with his fists in his hometown of Steelton, Pa., where he lived with his mother until last fall. He now lives with his father and stepmother.

"All my cousins used to fight people," the teen-ager recalled. "I just followed up on them. But I never jumped anybody. There weren't any real fights in Pennsylvania."

When Waters moved last fall to Maryland, he said, he found it difficult to adjust to the teen-age population at school. His stepmother, Karen Waters, a teacher in the District, said Waters "would always talk about how he couldn't believe the way they jumped people."

The trouble began in woodshop class two days before Christmas. A student described by a teacher as about six feet tall and weighing more than 180 pounds thought Waters had stepped on his shoe and ordered him to wipe off the scuff mark. Waters, at 5 feet 6 inches and 148 pounds, refused.

The bigger youth, egged on by five friends, "told me he would hit me so hard I would be seeing lightning," Waters related.

Water's father, Melvin, who is angry over his son's expulsion, said fear drove his son to break the rules. That fear mounted after two shoving incidents, one in the crowded school cafeteria and one in front of the school. Ultimately, the younger Waters said, he was warned by a friend to expect to be jumped by the group.

He went to school armed with the nunchaku, which he said he made to decorate the poster in his bedroom of martial arts hero Bruce Lee. "I was just taking them to let them know I wasn't scared. I knew what I was doing," Waters said.

When the fight finally broke out in front of the school, Waters said, he retrieved the nunchaku from a bush where he hid it that morning and swung it to hold off the six boys who he said had surrounded him. One youth took the weapon out of his hands, he said. Although no one was hit with the sticks, according to a school report, several punches were exchanged.

Clark Estep, executive assistant to school Superintendent Edward J. Feeney, held a conference on the Waters case with Waters, his stepmother and father, school disciplinary officials and the principal last Wednesday. A decision on the expulsion recommendation is expected by the end of this week.

Waters has not been allowed to return to school since Jan. 4. If he is expelled, as has happened in more than 80 percent of the cases under the new rules, his parents can appeal to the school board. The board has upheld all but one of 10 appeals heard through last December.

An appeal of two expulsions from Suitland High School were filed in December in Circuit Court in Upper Marlboro.

Waters' stepmother vows to fight the expulsion in court if necessary. "I can't accept it," said Karen Waters, faced with the prospect of placing Melvin in private school or in a public school outside the county. "I will take all my money out of my savings account and fight it."