Keeping the school door open to all children

A series of good results ought to follow the US Supreme Court's ruling that young illegal aliens may not be excluded from the free public schooling available to other children in America:

* In the specific instance of Texas, which sought the exclusion, all children will remain eligible for free public education. Illegal aliens have been included under lower court order since 1980. It was good to hear Governor Clements say the state could continue accommodating them without undue strain. (Most of those entering the US illegally are said to be single adult males without children anyway.) The governor not unreasonably suggests that federal funding assistance is warranted, since failures in federal enforcement of immigration law have contributed to the increase in illegal aliens.

* Other states now will be deterred from discriminating against alien children, as some were expected to do if Texas had won its case.

* The children themselves will not have to suffer denial of education. This not only could harm them but, as a judge in Houston warned two years ago, could ensure ''that most of them will become wards of society.'' Or it could risk the cynical interpretation of encouraging the formation of an underclass as a ready source of cheap labor.

* In a larger sense, the whole budget-beleaguered American school system should take heart from the Supreme Court majority's reasoning. In the face of all the current slicing away at education, it offered a ringing reminder of ''the importance of education in maintaining our basic institutions, and the lasting impact of its deprivation on the life of the child.'' So central was the educational argument that it seemed unlikely the ruling would automatically open the gates to welfare or other noneducational benefits for aliens.

To be sure, America's schools have a long way to go toward meeting the ideal of equal educational opportunity. Some children of illegal aliens are still kept from public schools through their parents' fear of exposure.

But the Supreme Court has acted in the nation's best tradition of equal protection of the laws - and enlightened self-interest - by ensuring that the talents of no child be lost through being turned away at the schoolhouse door.