There's a renewed rallying to give tuition tax credits to parents of students attending private and parochial schools. The new charge up Capitol Hill is led by President Reagan, who says he'll attack the issue Teddy Roosevelt, ''roughrider'' style. He insists the time has come to bail out nonpublic schools and, in particular, parents who he says are unfairly ''supporting two school systems and only using one.'' The President also favors a voucher system ''to help parents of disadvantaged children.'' These government vouchers could be used at any school, public or private.
Why might tuition tax credits and/or vouchers get further in Congress this term than in the past - when advocates of church-state separation clobbered them with the resounding force of the First Amendment?
Two reasons: (1) the beleaguered state of US education today; and (2) the state of mind of the US Supreme Court, which is buffeted by conservatives seeking legal cracks in the long-impenetrable ''wall'' of separation.
Tax-credit advocates have latched on to the much-publicized report of the National Commission on Excellence in Education (NCEE) which emphasizes the declining performance of high school students.
Sen. Robert Dole (R) of Kansas, chairman of the Senate Finance Committee, which is holding hearings on the costs of credits, insists that ''a strong system of private schools available to all income classes should contribute to a better education for all of the children.''
Under the administration's plan, parents with incomes below $60,000 who send their youngsters to private elementary or secondary schools could claim tax credits on a sliding scale: up to $100 this year; $200 next year; and $300 thereafter. It could cost the federal government $779 million in revenues by the end of 1987.
Also pointing to the NCEE report (which, incidentally, doesn't mention tuition tax credits) in advocating ''parochaid'' is Robert Smith, executive director of the Council for American Private Education. He suggests the federal government owes every child the opportunity to get the education that his parents think best, even if this means underwriting private schools.
And Education Secretary Terrel H. Bell - leader of the administration's fight to persuade Congress to pass the tax-credit legislation as well as a voucher plan now before the House - says these two bills ''would lead to a significant improvement in educational opportunities for . . . deprived children by offering a wider range of choices to parents and students.''
Opponents such as Sen. Daniel P. Moynihan (D) of New York say tuition tax credits won't solve the nation's educational woes. And Sen. John H. Chafee (R) of Rhode Island notes that the program wouldn't even require private schools to accept handicapped and special-needs students, whose education is the most costly to public schools.
Others reject the idea on constitutional grounds. Rep. Kent R. Hance (D) of Texas, a conservative Southern Baptist who backs Reagan on tax cuts, says of the tax credits: ''It is the duty of the Congress to reject this radical idea, which could turn our nation's traditional concepts of separation of church and state and support for public education inside out.''
And James Dunn - representing both Americans United for Separation of Church and State (AU) and the Baptist Joint Committee on Public Affairs - said in testimony before the Senate Judiciary Committee: ''No one can escape the conclusion that public funds for parochial schools benefit the sponsoring church. The net result is that the taxpayer is forced to subsidize religion, and overwhelmingly one brand of religion at that. Seventy-five percent of church-school students are in Roman Catholic schools.''
Regardless of whether or not Reagan's charge up Capitol Hill is successful, tuition tax credit combatants are closely watching how the Supreme Court resolves a related issue involving a Minnesota law which allows parents of both public- and private-school students to deduct costs of tuition and fees from their state income taxes.
The high court, which has in the past flatly rejected cases of this type on the grounds that such plans are unconstitutional subsidies of religion, recently heard oral arguments on this case. Attorneys for those opposing the Minnesota law note that most beneficiaries are parents of parochial-school students, since enrollees in public schools seldom pay tuition. But Minnesota's attorney general argues that since the statute benefits both the private and public sectors, it is ''neutral'' and ''secular'' in purpose - and not in violation of First Amendment church-state bars.
Minnesota's law was upheld by one federal appeals court, while a similar program in Rhode Island was struck down by another. Hence, the need for Supreme Court resolution.