President Bush visited Montgomery Blair High School yesterday for a town hall-style meeting to discuss his plan to partially privatize Social Security -- an appearance that drew about 400 protesters outside the Silver Spring school.

The loudest voices came from some Montgomery County residents and Blair students who questioned why they were not allowed inside. They were kept far from the president, but their shouts and beating drums could be heard by some of the 500 invitees waiting to pass through security.

Although Montgomery police officers tried to confine them to one area, many of the demonstrators broke away and briefly disrupted traffic on University Boulevard. "I feel like he's kind of trespassing," said Katie Frank, 16, who will be a Blair senior next school year. "He should know we don't support him."

Trent Duffy, a White House spokesman, said blocks of tickets were distributed to several nonprofit organizations, including Young America's Foundation, which selected the individuals who received them. The event was organized by the National Retirement Planning Coalition, a financial industry and advocacy group. Comedian and author Ben Stein, a Blair alumnus, is the group's honorary chairman.

Duffy said he did not know if any of those invited were county residents. "Once we give the tickets to the organizations, the White House doesn't ask for residency information," he said.

Bush said the Montgomery meeting and similar events across the country are important opportunities for him to explain his plan, which would give workers a chance to divert some payroll taxes to private investment accounts.

Bush said the system should be improved for younger workers, giving them "the ability, if they so choose, to take some of their money -- after all, it's your money in the payroll taxes -- and set it aside in what we call a voluntary personal savings account. . . . I like the idea of giving somebody a chance to build a nest egg that the government can't spend."

U.S. Rep. Chris Van Hollen (D-Md.), a possible candidate for Senate next year, joined County Executive Douglas M. Duncan (D) and state Sen. Ida G. Rubin (D-Montgomery) at a news conference outside the school to speak out against Bush's Social Security plan. Duncan is expected to run for governor.

Van Hollen said Bush should return to the school in the fall to talk to Blair students. "The president has very carefully scripted these meetings," he said after the news conference.

Staff writer Jim VandeHei contributed to this report.

Outside Montgomery Blair High School, demonstrators criticize the president. At center with cane is Marion Lane, who was angry that a public school was being used for the speech but that the general public wasn't invited.