IT IS JUNE, schools are about to close and tens of thousands of Washington teen-agers are eager for work - but they are terribly frustrated in their attempts to find it. Many who have been standing in long lines and filling out intimidating application forms see nothing ahead but rejection and the bleakness of a summer without a job. It is this city's most pressing problem - and it will take every sensible, urgent response that Mayor Barry, Congress, the White House and the business community can muster to do something about it in time.

Most crucial is how Sen. Patrick J. Leahy (D-Vt) and Congress react - not because the District is simply relying on federal handouts to take care of things, but because the city government cannot even spend it own taxpayer's money for a jobs unless Congress gives permission. Mr. Leahy is chairman of the Senate subcommittee now considering a city proposal to provide about 8,500 jobs for youngsters and 1,500 year-round jobs for youths as well as adults. It deserves full and immediate approval.

Sen. Leahy did react quickly with a hearing. The next measure of his concern will be the subcommittee's response. On this, the senator has replied that "it is conceivable that the full amount might not be appropriated." Why? According to the senator, there are some uncertainties on Capitol Hill about Mayor Barry's ability to meet his goal of providing 30,000 summer jobs; and there is a desire, especially in the House, to hold the line on government spending. "There's this feeling in the Congress about balanced budgets and all. Unfortunately, a lot of good programs suffer because bad programs have been funded in the past. And the District is not one of the favorite budgets up here."

Hold it right there: These congressional excuses are as flimsy as they are harmful to the well-being of the city. Again, we're talking here about locally raised revenues as well as other funds, which a locally elected government should be able to use for emergency efforts to do something about a community crisis. Besides, whatever doubts Congress may have about Mayor Barry's ability to deliver on his promise, he certainly can't do it if Congress doesn't let him try. And it is deceitful to use denial of these summer jobs sought in a local city budget as a way for members of Congress to show off for unaffected citizens in their home districts, piously referring to this as a case of curbing government spending and of balancing budgets. As for the unpopularity of the District's budget "up here," should the city be punished because its submits its budget to Congress as required?

Sen. Leahy should take the lead in impressing upon his colleagues in both houses the importance of giving an immediate go-ahead to the summer job effort before it is too late.