Taxpaying residents of the District of Columbia without children in school may have concluded that they have no stake in the local election on Nov. 3, but nothing could be further from the truth. If Initiative No. 7 authorizing an educational tax credit passes, the result will be a sharp increase in everybody's taxes, with the exception of those families with children in private schools.

Older homeowners living on fixed incomes have particular reason to be aware of the financial implications of this initiative, ignoring for the moment the educational arguments that have dominated most of the debate thus far.

The initiative is complicated and subject to interpretation on certain points, but in essence it provides a 100 percent credit against D.C. income taxes up to a maximum of $1,200 per taxpayer for the educational expenses of a child enrolled in a private elementary or secondary school. There are currently more than 20,000 D.C. children enrolled in private schools whose parents would benefit from this credit.

The revenue loss to the District government cannot be estimated precisely, in part because it is uncertain whether more than one taxpayer can claim a credit for the same child. However, responsible estimates range from a cost of $25 million to over $70 million per year.

Note that there are no offsetting savings from this credit for the city's budget. The tax benefits mentioned above would go to parents whose children are already enrolled in private schools. The credit operates like a new spending program in that all taxpayers would now be helping to subsidize private-school tuition.

If these families were particularly needy, there might be a reason on social grounds to help them pay private-school tuition. As a group, however, families that currently can afford private schools are hardly candidates for public handouts. And for those with low incomes, the credit is of little value because it is limited to the amount of their D.C. income tax liability. A family of four with a $7,500 income, for example, pays about $125 in D.C. income taxes, and that would be the maximum tax credit it would receive.

Faced with a revenue loss of 25 to 75 million dollars annually, the city would have to either cut services or raise taxes by a like amount. Mayor Marion Barry has stated clearly that he would seek to raise taxes by the amount of the revenue loss. A $25 million revenue loss would translate into a 10 percent increase in property taxes.

Taxpayers must decide whether they are willing to pay 10 percent more in property taxes to subsidize private-school tuitions. If not, a no vote on Initiative No. 7 is the answer.