St. Alban's School, a private school for boys affiliated with Washington's Episcopal Cathedral has more topscoring students this year in a national scholarship contest for blacks than any other high school in the Washington area.

The five semi-finalists at St. Alban's - half the blacks in its senior class - are among 27 students at private schools in Washington who received top scores in the annual National Achievement Scholarship Program for Oustanding Negro Students.

By contrast, the District's public schools, which enroll about 10 times more black students, had only 14 semi-finalists in the contest.

In the Maryland and Virginia suburbs 11 private school students and 27 in public schools were named semi-finalists.

Among Washington's public schools, those with the most semi-finalists - four each - were McKinley High in Northeast and Wilson in upper Northwest. Springbrook High School in Silver Spring (Montgomery Couny) had three semi-finalists.

Two private schools also had three semi-finalists a piece - Sidwell Friends in Northwest Washington and Takoma Academy in Takoma Park, Md.

The relatively large number of blacks in private schools who score high on the national tests - even though relatively few blacks are enrolled in them - is part of a pattern in the test results for the past several years.

"We're getting some awfully good black students now," said the principal of one private school. "And that's something of dilemma, you know. I hate to take good kids away from the D.C. public schools. But everyone is entitled to the best education he can get. There's no easy answer. But I think the Distrist is now really trying to improve its schools."

The semifinalists were picked on the basis of a 100-minute multiple choice examination in England and mathematics, sponsored by the National Merit Scholarship Corporation.

About 60,000 black students throughout the country took the test last fall. There were among about 1 million high school juniors taking the exam, which is similar to the Scholastic Aptitude Test (SAT) of the College Entrance Examination Board.

Last month about 15,000 students with the highest scores - regardless of race - were named as Merit Scholarship semi-finalists. This week the highest-scoring black students, about 1,500 nationwide, were named as National Achievement semi-finalists.

According to the published lists of winners, six black students in the Washington area scored high enough to qualify as Merit semi-finalists as well as semi-finalists in the achievement program. Last year only one black student did so.

Five of the black Merit semi-finalists attend private schools in Washington - Bryan H. Fortson, Georgetown Day; Melaine Gross, Immaculata Prep; Phillip a Jones, Sidwell Friends; Constance M. Smith, Academy of Notre Dame and Charles A. Wood, St. Anselm's Abbey. The sixth, Liane G. Rozzell, is a student of W. T. Woodson High, a public school in Fairfax County.

Next spring about 575 students throughout the country will be chosen for National Achievement scholarships. Most of them are given by companies and universities.

Among the semi-finalists in Maryland, 13 attend public schools in Montgomery County and in Prince George's county. In Virginia the Fairfax County schools had six semi-finalists, Arlington and Alexandria, none.

Last year Washington's public high schools had about 25,000 black students, compared to about 2,200 in private schools.

McKinley High, the four semifinalists came from a class of about 800 black students and only three nonblacks - one white, one Hispanic, and one Asian. At Wilson, the four semifinalists are in a class of about 400 blacks, and 300 whites, Hispanics, and Asians.

At St. Alban's, which is selective and expensive (about $3,000 a year), although it has some scholarship students, the 10 blacks are part of a senior class of 71.

According to a survey of both public and private schools, many of the National Achievement semi-finalists have college-educated parents, most of whom are professionals or mid-level civil servants. School officials said some of the semi-finalists have parents with non-professional jobs - including at least one barber and one janitor, but the preponderance of them seem to have middle-class backgrounds. At the private schools, officials said, only a few of the semi-finalists are receiving financial aid.

Below is a listing of Washington D.C. students who have qualified as Achievement Program Semifinalists. The final awards will be announced, March 22, 1978.

Constance M. Smith, Academy of Notre Dame; Erik P. Christian. Archbishop Carroll High School; Roxanne L. Bland and Brian D. Tate, Duke Ellington School of Arts; Robert K. Harper, Frank W. Ballou High School; Haidar B. Ali and Bryan H. Fortson, Georgetown Day School; Wanda E. Fleming and Lena D. Mitchell, Georgetown Visitation Prep School; Sebastian P. Hall and Earl MacFarlane, Gonzaga College High School; Melanie J. Gross and Martha D. West, Immaculata Prepartory School; Joann M. Hamilton and Myra E. Somerville, Immaculate Conception Academy; Angela E. Jones, La Reine High School; James L. Matory, Maret School; Steven H. Eversley, Dolores E. Hill, Lillian L. Loman and Tamarie S. Watson, McKinley High School; Greta Y. Duncan, School Without Walls; Cheryl A. Bascomb, Leigh A. Jackson and Phillip A. Jones, Sidwell Friends School; Donald L. Galloway, Spingard High School; Brett A. Baugh, Donald Cureton, Kwabena Gyasitwum, Michael J. Perry, and Darryl L. Webster, St. Alban's School; Charles A. Wood, St. Anselm's Abbey School; Karen M. Johnson, St. Anthony's High School; Michael Wilson Reed and Ronald R. Ross, St. John's College High School; Isabel A. Wilkerson, Theodore Roosevelt High School; Babette Dickerson, Washington International School; Pamela A. Allen, Dana W. McGinty, Donald A. Pierce and Chita T. Taylor, Woodrow Wilson Senior High School.