The business establishment is about to invest more than $1 million in the District of Columbia's public school system--a figure that is expected to grow in future years--and the most frequently asked question is: Why?

"Enlightened selfishness," is the answer provided by Washington consultant Paul S. Forbes, a former executive with Giant Food Inc. and Drug Fair who has been advocating such business involvement in this community for the past two decades.

When he met new Washington School Superintendent Floretta D. McKenzie earlier this year and discovered a public official who welcomed participation by private enterprise in the business of us all--education--he became an activist for her ideas, Forbes recalled last week.

In his view, the concept of national and local corporations sponsoring and helping to manage career high school programs in jobs sectors where the economy is growing is an opportunity for business at just the right time.

The business community is enjoying a respite from antibusiness attitudes and unless business can make the taxpayers feel that recent tax benefits for business will have a tangible pass-through" to the general society, "after the Reagan administration there will be more onerous regulations because of disillusionment," Forbes asserted.

What business cannot afford is to take the attitude that "they have the goodies now . . . and they don't have to do anything but give to their favorite charities," he added. "There is a distinct difference between voluntarism or giving to charities, and really solving problems."

The problem, which is inadequate public school education, must be tackled. And the beauty of the investment plan proposed by Superintendent McKenzie and her assistant for corporate affairs, Pete Weaver, is that specific gains and benefits for business can be the result. There is potential profit in this for the business community, for D.C. youngsters of today and tomorrow and for public education as a vital part of American society.

McKenzie has articulated her appeal for a partnership to such companies as General Motors, Control Data, Marriott and Xerox in a candid way that hard-nosed business people appreciate:

"Economic fundamentals are changing rapidly, altering the very rules of corporate investment. Public and private markets are shifting, inflation is rampant, and competition is increasing at home and from abroad. At its current growth rate, technology is doubling every seven years so that today's students are required to learn more than twice as much as they were 10 years ago. Human capital is at a premium and will become more so. We are not seeking philanthropy; we are seeking partners to invest in developing the human capital that is required by corporate America for productivity, profitability and growth."

In McKenzie's view, America's schools are failing to provide students with basic skills not just in reading, writing and arithmetic, but in attitudes and work habits. "Businessmen who try to remedy the problem in-house may be wasting money," she says. "Most corporate training efforts are unfocused, with corporations transplanting to their offices those practices that didn't work in the public schools."

To cite one example, Metropolitan Life Insurance devotes more than 40 percent of its training and development budget to the teaching of basic English usage and math.

McKenzie wants to break this cycle and she wants to start in the District, with a series of model career high schools that have the potential of becoming so good that suburban residents in Maryland and Virginia may end up sending their kids into the D.C. school system (and paying tuition). Even modest success would begin attracting families back into the city or stopping the outflow of families from the city when children reach school age, Forbes commented. With the new schools opening next fall, success could start very quickly given the corporate power involved.

In previous years, Forbes noted, the difficulty in developing a proposed public-private partnership embodied in McKenzie's plan has been the sour relationship between governnment and business. Private sector involvement always brings with it suspicions about motives, especially in Washington where blacks long were excluded from the real business establishment.

In this case, the motives are up front and boldly stated for all to see: Business invests time and money in a better public school system so that it can save lots of expenses in the future on basic education, training and rapid turnover of unskilled workers. Some of the firms involved seek highly skilled black professionals for their businesses and see a plan of action. The D.C. schools program, if successful, would certainly be copied in other cities and that would develop the real return for national businesses on their initial investments here.

And, as Weaver noted, the D.C. schools are ready and anxious to publicize the new interest in public education by corporations--a commodity more valuable than a box of gold bars in image-conscious Washington, because of government policymaking and the communications industry concentration here.

The basic outline of McKenzie's program is very simple:

* The stated goal is to improve education and career options for D.C. public school graduates by increasing their human capital for competitive markets within a free enterprise economy. The school system now has about 95,000 students, most of them blacks.

* A key strategy will be to augment standard academic work with career programs on which major employers will collaborate through investments that can be cost-justified to stockholders, taxpayers and the students.

* Model high schools in engineering, computer sciences, communications, hospitality and finance/insurance will be organized under the direction of a prime corporate sponsor, much like a business subsidiary. Other companies that employ persons in specific sectors will be asked to invest and to share in staffing and management, development of curriculum, providing modern facilities and equipment and creating jobs programs for the students.

The last point is one of the most attractive elements in the D.C. school system plan. For example, a three-semester program could be developed at one of the new high schools that involves full-time work one semester and school during the remaining semesters. Part-time and summer jobs opportunities can be developed in various sectors.

But the longer-range implications are even more encouraging. It is clear, for example, that auto giant GM wants to get involved in the D.C. program despite its current woes in the midst of recession. GM professionals will help develop engineering programs and take part in the teaching. You can bet that GM's people will be watching out for the talented high schoolers and helping them get enrolled at a college or university for engineering degrees and possible jobs with the Detroit firm.

Says McKenzie: "Everyone has asked, 'What's in it for us?' Well, we're in a bargaining mood. . . . We expect to negotiate contracts with corporations based on mutual interests and we expect to be held accountable for our performance. Because education is our business, it's time to do it in a businesslike way. . . . This is an investment in human capital that has widespread implications for our city and the nation. . . . Redirecting even a small percentage of the billions of dollars now spent on corporate hiring, turnover and training can inure to the benefit of the entire nation."

It is important for leaders of Washington business to understand that the D.C. schools program is not just for giant corporations. There's so much to be done that any company's involvement would add up to more than just a contribution.

A good example is the advertising firm of Goldberg/Marchesano and Associates Inc., one of the largest in its business here but small by national standards. In recent years, this ad agency has been the talk of the town at Christmas for a "rather rowdy party," to use the apparently mild description of Senior Vice President Karen Kershner. Last year, the event attracted more than 600 persons. This year, the party is off and the money ($20,000) will be put into the D.C. schools.

In a memo to their staff, Norman Goldberg and Carole Marchesano said: "First, we aren't after a reputation as wild party-givers. Times and expectations have changed. . . . These parties are, for example, inconsistent with the important work we have done in alcohol and drug abuse prevention. . . . In these difficult times when those least able to afford it are facing dramatic cuts in their standard of living, publicly flaunting an image as lavish party-givers is almost obscene."

Under a formal agreement with McKenzie, the ad agency will work on development of a communications-career high school, to focus on broadcasting, advertising, journalism, public relations and lobbying. The firm's money will be used to develop showcases (film festivals, art fairs) to recognize student achievements in communications; for advertisements to inform business about the new D.C. program, and for radio-TV spots that use D.C. students and school facilities.

Goldberg/Marchesano also will work on attracting other firms in its industry to help with the communications high school, work with the school system on curriculum, begin assembling instructors and expert lecturers to assist D.C. teachers and to conduct seminars for teachers and students, provide assistance in design and building of such needed facilities as broadcast studios, and work in the private sector to develop job internships, scholarships and summer career-oriented jobs.

"We didn't just want to write a check and walk away," said Kershner. "We wanted something to stay active and involved with."

As Weaver said, all of this is "very much on the cutting edge" of what may be evolving as a new acceptance of business as expert partners in the necessary rebuilding of confidence in public schools. Washington business is particularly lucky to have a chance at taking part in what could be a historic model for the nation.