About 650 undergraduates at J.E.B. Stuart High School in Fairfax County were given a choice yesterday of three punishments for participating in a March 25 walkout in support of their teachers' salary demands.

School officials, conducting three separate mass meetings ordered last week by a federal judge in Alexandria, gave students the option of a five-day suspension, a three-day suspensin with a written essay on their involvement in the protest, or a one-day suspension with 20 hours of volunteer work at the school this summer.

The "vast majority" of the students elected to take the three-day suspension and essay, according to a spokesman for the school's Parent-Teacher Association.

The suspension will take effect on Thursday. Stuart Principal Richard W. Johnson yesterday told the students they were free to appeal their punishment, and assured them that appeals would not jeopardize upcoming final exams.

At a similar mass meeting last Friday, 160 Stuart seniors also were given three-day suspensions and told to write an essay on their involvement in the walkout. The seniors were given credit for three days of suspension they served before the court ruled.

The protest was the largest of a half-dozen such boycotts in Northern Virginia schools, and coincided with a false fire alarm at the school that emptied classrooms and led to confusion among the students about whether to return to class.

U.S. District Judge Albert V. Bryan Jr. cited that confusion in overturning the suspensions last week and ordering hearings by school officials before penalties could be imposed.

Several parents remained irritated yesterday by the students' punishment.

"It's a sad statement on our school system when they are supposed to be teaching our children the principles of American democracy and they have to be taken to court before they understand the rules concerning due process," said Kenneth Kornher, the parent of a junior.

Mary Henderson, the mother of two suspended students, came to the hearings armed with a student code book.

"It says here that a student can be suspended for up to five days for being violent or carrying a concealed weapon on school premises. I could see one day of suspension, but this is just too much," he said.

But no one was more confused than Norasack Paphammabong, 16, a native of Laos who barely understands English.

"He came out of school when he heard the fire alarm," one student said. "When he tried to ask someone what to do, they told him to go home. He's been suspended, too. It just doesn't make any sense."