THE MARYLAND Board of Education's decision to push for tougher graduation requirements for its 220,000 high school students is timely and welcome. It should send a signal to local school districts throughout the state, some of which have already imposed higher graduation standards, that it is time students work harder for a more valuable high school diploma.

The best change the board approved will increase the amount of required math from two years to three. The current standard of 20 credits for graduation will not be expanded, but the number of mandatory credits will increase from 12 to 15. At first glance, this appears to be a smart move designed to make high school students spend more time on core subjects and less time on elective courses that may be relatively unimportant. Depending on what curriculum changes local school districts have already made, however, that might not be the case.

The state board has decided to require that high school students take one year each of fine arts courses and "practical arts" courses -- home economics, vocational education or industrial arts. So while adding one more core subject requirement -- the additional year of math -- the state board has added two years of requirements for students who might be better served by other choices.

Obviously, vocational education and other courses that can lead to employment in skilled trades are essential. But when done successfully, these are costly and intensive programs. It would only weaken their effectiveness for the students who want vocational programs if such courses are diluted by adding thousands of students who are uninterested in pursuing them. Some Prince George's County school officials are also concerned that the need to hire more instructors for fine arts and practical arts will decrease the number of positions they can fill with core-subject teachers.

The state board approved some other changes, most of them useful. A certificate of merit will be awarded to students who have maintained high grade averages while taking several advanced courses. Seniors will have to fill four credit requirements in their last year of school, which should make that last year less of a joyride. But before the board takes a final vote in June on the full package of these changes, it should realize that some of them will not necessarily result in a better education. Simply adding more requirements doesn't always help.