WHILE THE CITY anxiously awaits word from Congress on the fate of a crucial local summer jobs effort, the number of teen-agers seeking work continues to climb dramatically: As of yesterday, nearly 40,000 had registered, and city officials expect the total to hit 50,000 before the month is out. But how many of them will actually find work? And where should they - and the rest of the community - be looking for more help?

Mayor Barry remains determined to come up with the 30,000 jobs he promised to find - though a good 8,500 jobs hinge on the budget proposal now before a subcommittee headed by Sen. Patrick J. Leahy (D-Vt.). For the information of any doubters on Capitol Hill, Barry administration officials say they have now identified 25,000 jobs and are seeking at least 5,000 more to meet the mayor's goal. So there should be no question in Congress that an immediate approval of the budget proposal would produce important, tangible results.

Nevertheless, there remains the troubling prospect of yet another 20,000 or so teen-agers who want to work and may not be able to. Even though the private sector of the city has always participated enthusiastically in the summer job campaigns, an extra effort is urgently needed. Those teen-agers who are out looking for work right now and who will be tomorrow's work force in ths city cannot continue looking to the government - District or federal - to be the dominant employer in this town anymore. In fact, a majority of the jobs here already come from the private sector - and therein lie some interesting facts.

In the adult job market, statistics from the Metropolitan Washington Council of Governments show District government employment decreasing and federal hiring leveling off. So it is unrealistic to direct too many young people into the government. But consider these fields: Jobs in health services in the city - in hospitals, medical offices, supply firms and so forth - have increased by 58 percent in the last eight years; business services - from typewriter repairs to computer maintenance - are up 31 percent; and jobs with membership organizations, from file clerks to executive directors of trade associations, etc. - which last year totaled 32,000 jobs in the city - rose by 19 percent. Still other fields are growing: banking, educational organizations and legal services.

D.C. Council member Betty Ann Kane, who has been working with the Council of Governments' job-study committee, points out that these growing markets - the private industries that are enjoying a boom in Washington - should take a good look at the pool of local talent for the future. They can begin now. There are bright and willing young people ready for the opportunity to produce. How many firms have really done all they can this summer?