President Reagan today combined a warning that "education must never become a political football" with campaign-style rhetoric emphasizing a return to basics in classrooms, merit pay for teachers and another slap at the nation's largest teachers' union.

In the most comprehensive of a series of speeches on education issues, he appealed to the 87th annual convention of the National Parents and Teachers Associations to "send a message to Washington . . . and make it loud and clear. Tell them you want the basics in your schools and the parents back in charge. Tell them education must never become a political football because your children come first--and they must come first."

"Instead of worrying about whether we put together a Republican plan or a Democratic plan, can't we join together on a course of common sense for an American plan?" Reagan said to applause from the 2,500 delegates.

In a clear if indirect reference to his Democratic critics, Reagan added, "Let us stand together--parents, teachers, concerned citizens--and say no to all those who would divide, delay, and drag us down."

Political overtones and motivations were unmistakable in both Reagan's speech and the rush of Democratic presidential hopefuls to meet him head-on in the debate over education, which suddenly has become a hot political issue.

The speech today climaxed several weeks of high-profile presidential campaigning on education. Advisers have said they hope Reagan can use his identification with traditional American values as a springboard for the 1984 campaign if he runs for reelection. He stuck by his few basic themes and did not offer new proposals, as the Democrats have.

In his generally well-received speech, Reagan called for a "much greater emphasis on the basics," including improved standards, learning skills and "basic values of parental involvement and community control."

In a double-barreled approach to the nation's teachers, he first praised them.

"For too long, teachers have been fighting a lonely war and it's about time they got some reinforcement from the rest of us," he said. "It wasn't teachers who created and condoned the drug culture, sexual license and violence in our society. It wasn't teachers who encouraged the banality of TV over the beauty of the written word."

But Reagan, who has been campaigning for merit pay for teachers, again confronted the leadership of the National Education Association, which has opposed merit pay schemes as unworkable and prone to favoritism. Saying the NEA leadership is "mistaken," Reagan asked, "If we test other professionals, why shouldn't we test the people who will be responsible for teaching our children?"

He warned that the NEA, which has been active and influential in Democratic Party politics, could delay or block merit pay proposals that "the country wants."

The president dodged the issue of tuition tax credits. They are opposed by the PTA, as demonstrated by badges worn by some members here. A passage in Reagan's speech endorsing tax credits for parents who send their children to private schools was excised from the text at the last minute, and he made only an oblique reference to the need for "greater competition" in the schools.

But he received the only standing ovation today with a spirited endorsement of voluntary school prayer, which public opinion polls show enjoys wide support.

In focusing on his back-to-basics theme, Reagan noted the nation's accomplishments in sending men to the moon and challenged Americans not only to reverse the long decline in College Board testing scores but to "raise verbal and math scores at least 50 points--and do it within the next decade."

But Reagan again rejected new infusions of federal aid as an answer to school problems. Contending that federal aid to education increased almost 600 percent between 1960 and 1980, he declared: "If a 600 percent increase couldn't make America smarter, how much more do we need?

"I believe common sense tells us we don't have an education problem because we're not spending enough, we have an education problem because we're not getting our money's worth for what we spend."

Reagan acknowledged that more money would be needed to improve teachers' salaries, but insisted that further expansion of federal aid to schools would be "an old road that leads to a dead end in learning."

PTA leaders praised Reagan's call for a back-to-basics movement, quality teachers and merit pay, but they objected to his view that the federal government should play less of a role.

Manya Ungar, the PTA's lobbyist in Washington, said she was concerned that "once more he was talking in terms of 'don't look to Washington' " for money.

"We know that pouring money into a program does not assure its success, but that's avoiding the realities that some urban areas face," she said.

Ungar said that many local districts have had to cut because of money binds and that many states are on the verge of budget deficits.

A recent poll done for the White House shows overwhelming opposition among Americans to Reagan's 1980 campaign pledge to abolish the Department of Education. Reagan has been silent on that pledge during this week's education speeches and appearances.