THE TUITION TAX CREDIT is a ludicrous point over which to hold up legislation as important as the Social Security bill. But the tuition credit has been attached to the Senate's version of the larger bill, and there the House and Senate conferees sit, day after day, quarreling over it. They have been able to compose their differences over the multibillion-dollar taxes for Social Security, but they have been unable to reconcile the matter of the $250 credit. To assist them in that endeaver, we offer a few thoughts on the merits of the credit.

It's a thoroughly bad idea in principle, and in practice it is far too small a benefit to make much difference to anyone. The idea is that a parent paying his child's way through college could take a $250 credit on his income tax. The Senate voted for it by a very large majority. Having hit the middle- to upper-middle income groups with the heaviest part of the new Social Security taxes, perhaps the senators thought it expedient to blow the same taxpayers a kiss with the tuition credit.

But the credit does the least good to the people who need it most: students from poor families, who are trying to work their own way through school with the help of scholarships and loans, and whose income is so low that they pay no tax on it. The tuition credit also opens up extemely difficult questions of definition - the definition of a colleges? If junior colleges, why not secondary schools? But that immediately gets into the forbidden area of subsidizing church-related schools.

Since it typically costs several thousand dollars a year to send a child even to a public college, it's hard to believe that a $250 tax credit is going to prove crucial to many people's educational opportunities. There is a simple and sensible way for th conferees to end their embarrassing indecision: by throwing out the tuition tax credit and getting on with the final passage of the Social Security bill.