High school students, meeting in a mock constitutional convention on Capitol Hill this week, adopted an amendment that would give Washington full voting representation in Congress.

The resolution was proposed by Natasha Pearl,17, a Wilson High School senior who admits to a personal motive: "I'd like to be the first voting female senator from D.C.," she said in an interview.

D.C. Del. Walter E. Fauntroy, whose office supplied Pearl and other area students with ammunition to use in debating the proposal, said its adoption "confirms my view that the vast majority of the people, once they become aware of this inequity, will suppport the amendment."

Fauntroy said D.C. delegates from Wilson and H. D. Woodson high schools to Convention II, as the mock student gathering is called, "encountered the same lack of awareness" that District residents are "subjected to taxation without representation" as supporters of his congressional resolution have in trying to round up nationwide support for a real constitutional amendment.

Pearl, of 1800 Varnum St. NW, and Wilson High junior Leslie Smith, 16 of 3225 33d Pl. NW, also had to "clear up confusion about why we were not asking for statehood," Pearl found.

She responded that while there is a need for the Capital to retain its special status as a federal enclave, "I am confident the Founding Fathers would have wanted three-quarters of a million people" to have a voive in Congress. When the Constitution adopted, there were only 14,000 residents here, she said, "and many of them were not citizens."

Noting that students "voted overwhelmingly in favor" of the idea, Fauntroy said, "I am confident that once people realize how much human rights are being denied here, they will react similarly. If we can get to the states, ratification will come quickly."

Fauntroy's measure won lopsided approval of the House Judiciary Committee two weeks ago and is scheduled to be debated on the floor of the House in about three weeks. Fauntroy said he is "cautiously optimistic" that it will get the two-thirds sanction needed to be sent to the Senate.

Convention II is the outgrowth of a civics project begun in New Rochelle, N.Y., about eight years ago by Boris Feinman, a political ectivist who wanted students to "experience the legislative process by doing."

Feinman, 62 who is wealthy enough to devote full-time to the project, began with a "city hall school" course in New Rochelle, then moved up to the Westchester County government in White Plains, the New York legislature in Albany, and two years ago, to the Congress.

Feinman, whose own philisophy is "just to the right of Reagan," asked his local liberal congressman, Rep. Richard Ottiger (D-N.Y.) "let me borrow Congress" during the 1976 Lincoln Day recess, and "we got it, literature."

With cooperation from House door-keeper James T. Molloy, delegates to the first Washington session played out their roles on the floor of the House chamber.

Since then, the program has grown from one high school to 40, in 10 states and the District. Its congressional supporters include area Reps. Gladys Spellman (D-Md.), Newton Steers (R-Md.) and Herbert E. Harris (D-Va.) and Sens. Daniel Moynihan (D-N.Y.), S. I. Hayakawa (R-Calif.), and Birch Bayh (D-Ind.).

In addition to the two District high schools, students from Winston Churchill, Walt Whitman, Holton-Arms, and Holy Cross Academy in suburban Maryland and Thomas Jefferson in Northern Virginia participated.

Of the 141 amendments considered during the three-day convention which ended last night, only two were approved. The D.C. representation issue passed by a vote of 182 to 16, and direct election of the president carried 116 to 32.

One of the proposals that failed, noted Russian-born Feinman, would have allowed a naturalized citizen tobe president.