The idea came to Missy Sien three weeks ago during her American history class at Reston's South Lakes High School.

The topic of discussion was the federal deficit, projected to exceed $200 billion next year, and what could be done about it. Someone suggested the government hold a fund-raiser. Sien, 16, a junior, said: "Why not a bake sale?"

So, this Saturday, Sien and the rest of her history class will do just that -- hold a bake sale and send the profits to the White House to help balance the budget.

"No one here seriously thinks this will buy an MX missile," said teacher John McMenamin. Instead, students say they're doing it on principle.

"The main reason to do this is not to raise money," said Greg Morgan, 17. "It's to get people to think."

"People on the outside are going to say 'God, I'm 36 and I don't even care about the national deficit, and look at these guys from South Lakes High School. They're 16 and they're trying to do something about it,' " said Kris Kenjesky, 16.

Pam Sterling, 16, said she will be bringing meringue cookies made from her mother's recipe. Shervette Bell, 17, will show up with chocolate chip cookies shaped like dollar signs.

Along with others from their class, they'll set up their card tables at the People's Drug store in the South Lakes Village Shopping Center off Sunrise Valley Drive from 10 a.m. to 5 p.m. Saturday.

"There are people in America who are starving, and all the president is thinking about is missiles," said Joyce Brown, 16, one of many in her class who is upset about what she sees as reckless government spending in spite of a deficit. "We have so many missiles now that we could blow up the entire world."

"Why does the government have to spend money on stupid things like toilet seats?" said Chris Pascoe, 18, of charges made in February by Sen. William S. Cohen (R-Maine) that Lockheed-California Co. had charged the Navy $640 per toilet seat for P3 Orion submarine-hunting planes.

Lisa Wilkins, 16, thought the bake sale was a great idea, but had one reservation about handing the profits over to the government. "Is it really going to the national deficit, or is it going to go somewhere else?"

According to Marlin Fitzwater, deputy White House press secretary, the registered check from Missy Sien's history class will be deposited directly into a special U.S. Treasury fund.

The fund was set up in the sixties to pay off the national debt, which was $1.709 trillion as of midnight March 21, the most recent available figure, according to a Treasury official.

Fitzwater said donations to the debt fund have ranged from $1 to thousands. "Some people just do it because they like to, or because they think it's right. Or, maybe, some people didn't pay enough income tax one year, and they want to make it up. They feel guilty."

Is Fitzwater certain the bake sale funds won't get lost in the tangle of government bureaucracy? "If they send it to the Secretary of the Treasury, or the U.S. Treasurer, it won't get lost. It'll be noted, and I'm sure they'll get a letter of thank you from the appropriate people."

From Reagan?

"Well," Fitzwater said, "they might."