Tuition at the major private universities in the Washington area will increase $200 to $400 for the next academic year, but at most publicly supported institutions the charges will remain constant or increase only nominally.

The increases at private colleges generally equal or exceed the average yearly increases for the past decade and they will push total costs of attending such institutions, including room, board, tuition and fees, into the $6,000 to $8,000 a year range.

Catholic University in Northeast Washington, for example, will raise undergraduate tuition by $300 next year, the fifth consecutive year of tuition hikes above $200 and the largest single increase of the decade. Undergraduates will pay $3,750 in tuition next year, up from $3,450 this year. At the same time, room rates will go up an average 5 percent -- an air-conditioned double room, for example, goes from $820 to $860 next year.

For students who entered as freshmen in the fall of 1976, the increase will mean tuition boosts totaling $800 during four years of undergraduate study.

Just a few blocks away and across the street on Michigan Avenue, Trinity College also plans a $300 boost to $3,400 a year.

Among the major public institutions in the area, four plan no tuition increases next year. Tuition will remain stable at Northern Virginia Community College, George Mason University in Fairfax County, Prince George's Community College and the University of the District of Columbia.

With a charge of $67.50 a semester for a full-time student, the University of the District of Columbia has the lowest undergraduate tuition of any area college, and a university spokesman said there are no immediate plans to raise it. Graduate students at UDC pay $243 a semester.

At George Mason, the basic tuition charge of $32 per credit hour for Virginia residents will remain the same next year, but all students will have to pay an additional fee of $1.50 per credit hour to cover such costs as student activities, athletics and bonded indebtedness.

Full-time students at George Mason pay tuition of $384 a semester for up to 17 credit hours.

Northern Virginia Community College will continue to charge Virginia residents $8.50 per credit hour, or $100 a quarter for full-time students, and $335 a quarter for full-time, out-of-state students.

At Prince George's Community College, the basic fee of $15.50 per credit hour for county residents will remain unchanged next year.

Howard University, which has a basic tuition charge of $775 a semester, has no firm plans for an increase, although a boost is still a possibility, according to a spokesman.

Effective with the summer session, Montgomery College will raise its rates from $22 to $24 per credit hour or from $300 to $325 maximum per semester for county residents.

Last summer, the University of Maryland Board of Regents tentatively agreed to raise tuition $50, bringing it to $670 for the 1979-1980 academic year, but a final decision awaits legislative action on the university budget. The regents will decide in May whether or not to raise room rates, now pegged at $1,019 a year.

Gallaudet College in Northeast Washington, the nation's only liberal arts college for the deaf, will raise its tuition $39 next school year, making the total tuition $684 a year. Gallaudet is heavily subsidized by the federal government.

At many of the private colleges, the steadily increasing tuition hikes have caused concern among some administrators that the schools may be on the way to pricing themselves out of the market.

Meeting in Washington recently, the National Association of Independent Colleges and Universities went on record as supporting full federal funding for tuition assistance programs designed to help middle-income students.

The decision reflects a concern of many private college officials that their schools may become institutions for only the very rich, who can afford the costs, and the very poor, who can get scholarships.

To counter this "middle-class squeeze," Georgetown University a year ago adopted a policy of seeing to it that every student admitted to Georgetown got some financial assistance -- either a scholarship, a federal grant, a loan or a work-study job -- if the student needed it. Officials say the policy has cost Georgetown $300,000, but they say it was worth it.

In addition, Georgetown has taken steps to help lighten the burden of yearly tuition increases. Once a student has been admitted, Georgetown maintains a dual tuition scale charging a higher rate to first-year students. Currently, freshmen and transfer students pay $4,100 in tuition. Others pay $3,900 a year. A university finance committee has recommended an across-the-board increase of $350 for next year.

At George Washington University, the Board of Trustees has approved an increase that will boost the academic-year tuition for most undergraduates to $3,200, an increase of $200. Law school tuition was raised $500 a year, to $4,100, while the fee for part-time undergraduates will rise from $110, to $117 per semester hour. For first-year medical students, tuition will be the same as this year, $11,800, the first time in more than two decades the medical students have not faced a tuition hike.

American University's Board of Trustees will act this spring on a recommendation to raise undergraduate tuition 10.57 percent, from $3,690 to $4,080. Law school students face a $400 tuition hike, to $4,100 a year, while graduate students face a raise from $129 to $143 per credit hour. CAPTION: Chart (TABLE) SCHOOL(COLUMN)TUITION 1979-80(COLUMN)INCREASE American University(COLUMN)$4,080(COLUMN) $390 Catholic University(COLUMN)$3,750(COLUMN) $300 Gallaudet College(COLUMN) $684(COLUMN) $39 George Mason University(COLUMN) $768(COLUMN)none Georgetown University(COLUMN)$4,450 *(COLUMN)350 George Washington University(COLUMN)$3,200(COLUMN) $200 Howard University(COLUMN)$1,650(COLUMN)none Montgomery College(COLUMN) $650(COLUMN) $50 No. Va. Community College(COLUMN) $300 **(COLUMN)none P.G. Community College(COLUMN) $372 ***(COLUMN)none Trinity College(COLUMN)$3,400(COLUMN) $300 University of D.C.(COLUMN) $135(COLUMN)none University of Maryland(COLUMN) $670(COLUMN) $50(END TABLE) (FOOTNOTE)

* For first year students (END FOOT)(FOOTNOTE)

** For three quarters (END FOOT)(FOOTNOTE)

*** Based on two semesters at 12 credit hours per semester(END FOOT)