STUDENTS LEAVE Maryland's public colleges after two years at a rate nearly twice the national average for public colleges. Maryland's four-year public institutions attract a relatively smaller number of top high school students from within or outside the state than most other states' public colleges. And those are only some of the signs of trouble in Maryland's public postsecondary education system.

For example, several of its campuses - notably, the University of Maryland's College Park campus - are overcrowded, while others are far below capacity. There is little difference between the admissions requirements - or, apparently in some cases, the quality of the curricula - for the 17 two-year community colleges and the six four-year state colleges. And several institutions are considering creating doctoral programs when, generally speaking, the need for doctoral programs has diminished greatly.

In short, some of Maryland's colleges are put out of step. They seem not to have noticed that the period of unrestrained growth in higher education has ended. Colleges face a different set of demands: in coming years, fewer students of traditional college age and more older and part-time students; less money for education at all levels of government; a tight job market that has made certain fields of study an unrewarding route to a job.

The year-old Maryland Board of Higher Education has produced a good blueprint for how the state's postsecondary education system can adjust to this new period of limited growth. The board wants to distribute students more rationally among both the different kinds of institutions and the different campuses of the state colleges and the university. It proposes to do that by, first, changing the admissions requirements to the different kinds of schools: The community colleges will continue to be "open enrollment" schools; the four-year institutions will become more selective. And, second, by developing special areas of study at different campuses to attract students to those campuses. For example, Morgan State University in Baltimore will have a special program in urban studies. The University of Maryland at Eastern Shore is developing an environmental and marine-sciences program. And so on.

The state board has the legislative authority for education planning in the state, but, to make the necessary changes, it must receive fiscal support from the General Assembly and the cooperation of college officials. Can the board upgrade the state colleges, most of which are still more like teachers' colleges than full-fledged liberal-arts institutions? Can it persuade parents and students that College Park isn't the only public institution in Maryland offering a good education? All one can say now is that the board's plan does offer a way for Maryland's public colleges to better serve the needs of the state's taxpayers - and its students.