THIRTY YEARS AGO, a majority of the Supreme Court accept Justice Hugo Black's sweeping pronouncement on the need to keep "high and impregnable" the "wall of separation" created by the First Amendment between church and state. That metaphor has come down through the years as a classic statement of principle for those who oppose government aid to religious schools, even though there was doubt at the time that the court would follow it literally.

Well, the court didn't follow it all that well. By 1971, the "wall" that had been so sacred to Justice Black had become, in the Court's language, "a blurred, indistinct, and variable barrier." Last week, in upholding most parts of an Ohio plan to aid private schools, the Court compounded the blur.

Although the Court, in its latest decision, was unabel to muster a majority for any one view of how the First Amendment's bar against the establishment of reigion should be interpreted, it held constitutional several parts of that plan. These permit the use of public funds to buy standardized tests and scoring services for private schools, to buy secular textbooks that are loaned to private-school students, and to provide those students with speech, hearing and psychological diagnostic and therapeutic services. The only limitation the Court set on those programs was that therapeutic services cannot be provided on the premises of a sectarian school. But it went on to hold unconstitutional two other parts of the Ohio legislation. These authorized the loan of instructional materials and equipment to private-school students and the transportation of those students on field trips.

If you have trouble figuring out the constitutional differences between those various kinds of aid, don't worry. So does almost everybody else. Only two members of the Court - Justices Blackmun and Stewart - agreed on all of them. Some of the other Justices voted to uphold all the parts of the Ohio program and others voted to strike all of them down. The key difference seems to be the willingness of Justices Blackmun and Stewart to tlet the constitutionality of such programs rest on whether they aid the students more than they do the school or vice versa.

It may well be that the test these two Justices have seized upon sums up accurately the meandering course the Court has taken in trying to decide what kinds of aid to sectarian schools are permissible. But it is a test that has little else to commend it. It encourages those who favor state aid to sectarian schools to try to find new ways to get money to them. And so the "wall of separation" can be expected to go right on crumbling. The result can only be precisely the one that the First Amendment's establishment clause was intended to prevent: the mingling of religion with government to the ultimate weakening of both. It is worth noting that to get the money that Ohio is now handing out, sectarian schools must give up some of their autonomy is selecting both students and teachers; they are now compelled to make no distinctions based on "creed."

For the time being, then, the door is open fairly wide to state and federal aid to sectarian schools, limited only by the ingenuity of lawmakers to devise new ways to skip over what's left of that "wall of separation." We think the Court was right the first time - when it was listening to Justice Black. The strict separation of church and state, to our mind, is a large part of what the First Amendment is all about.