To examine equity issues involving proposed Federal income tax credits for private school tuition, the author uses data from the Bureau of the Census and other governmental sources to estimate the effects of tuition tax credit (TTC) plans. After discussing equity and educational policy, he compares would-be TTC recipients--private school families with TTC eligibility--with all families of school-age children. Comparisons are based on type of school (public or private), school religious affiliation, educational level, geographical region of the United States, urban or nonurban location, family income, race, sex, and need for special or compensatory educational services. Using a hypothetical, typical TTC plan, the author analyzes the potential effects of TTCs if families shifted from public to private schools or from low- to high-tuition schools, or if private schools altered their fees or scholarship policies. The relationship of family tax liability to TTC plans is discussed, as are the adequacy of family resources for taking advantage of TTCs and the incentives for private schools to raise tuitions or reduce scholarships under TTCs. In his conclusion the author looks at the policy implications of his findings. (RW)