Boston — The Reagan administration is forcing many high school students to make a tough decision:
Should they finish high school, get their diplomas, and maybe lose their best hope for affording a college education?
Or should they accept the offer of some colleges and universities: ''Drop out'' of high school and we'll let you complete high school-level courses while working for your college degree?
The choice is being forced by pending cuts in education aid from Uncle Sam.
On May 1, social security benefits for an estimated 150,000 students dry up. They are eligible for education benefits because of retired, disabled, or deceased parents who were covered by social security. The benefits end when the child turns 18, but could continue for four more years to finance a college education if the child is enrolled in some post-secondary education by May 1.
At least four bills that would postpone the aid cutoff are in US House committees. One bill would put off the deadline until July 1, another until Oct. 1 (to include all students who planned to graduate after summer school), and yet another would repeal elimination of the benefits.
But the delays would be costly. To postpone the cutoff until Oct. 1 could cost as much as $900 million, if all eligible recipients took advantage of the social security extension for the full four years. The highest price tag on delaying until July 1 is estimated at $245 million.
Besides enticing students to leave high school, educators say the deadline is spurring another change: Some colleges and universities are willing to accept students without high school diplomas in order lure these students who can bring with them their own source of funds.
Among the novel ways they are enrolling high school students:
* At Pennsylvania State University, officials have set up a program in cooperation with high schools to allow seniors to start the spring term in early March. Students can take both high school and college-level courses at the same time, and the high schools guarantee graduation if set conditions are met. Up to 500 students are expected to take advantage of the special program at all 19 Penn State campuses, according to assistant dean of admissions Glenn Carter.
* At Nassau Community College in Long Island, N.Y., 400 would-be June graduates have taken advantage of an early admissions program that has been altered to help students facing the social security benefit cutoff.
* At Delta Community College in Saginaw, Mich., the summer semester will start a week early for social security recipients so they can beat the May 1 deadline. The rest of the students will start May 3, as scheduled.
* At Francis Marion College in Florence, S.C., Dean William Moran is sending out a letter to area high school guidance counselors to tell them the college is holding a special six-week ''summer session'' of night classes starting April 19 that is specially geared for students still attending high school during the day. The session is specifically designed to meet the criteria to qualify for social security benefits.
But despite these special efforts by colleges, hard questions still remain.
''We're struggling to strengthen the value of a high school diploma, and here's the US government interfering with that,'' says Robert Kruse, assistant director of government relations for the National Association of Secondary School Principals. ''Counselors are put in the dubious position of advising students to pull out of high school and enroll (in college) as soon as possible.''
Mack Jones, principal of Walterboro High School in Walterboro, S.C., says only two of his students already have dropped out of school completely in order to receive the social security benefits. But he agonizes over how to advise another 15 or 20 students affected by the May 1 deadline.
''You have to be realistic about it and let the students know there's nothing magical about a high school diploma,'' says Mr. Jones. ''I don't have any qualms of what to tell them: I'd tell them in a minute to drop out of high school and go to college. The problem is, the student can wind up with nothing if he doesn't make it in college. Then he may pass the exam for the Graduate Equivalency Degree, but there's also the possibility of not passing that. Then the student gets nothing.''