Religious leaders and senators alike were divided yesterday as the Senate Judiciary Committee opened hearings on a constitutional amendment to permit prayer in public schools.

"Our public school is not there just to teach children to read and write," but to inculcate other values as well, including "acknowledgment of God," declared Gary L. Jarmin of the Project Prayer Coalition. "What is unconstitutional is not the activity of prayer in public schools," he said. "What is unconstitutional is the lack of it."

But the Rev. Dean M. Kelley of the National Council of Churches called the controversial amendment, proposed by President Reagan in May, "unjust, unwise and unnecessary." The amendment, Kelley warned, "makes the rights of members of religious minorities dependent upon the self-restraint of religious majorities."

The amendment would override a 1962 Supreme Court decision that barred prayer in public school as a violation of the First Amendment, which prohibits "an establishment of religion."

The measure provides that nothing in the Constitution "shall be construed to prohibit" prayer in public schools or institutions, but bars state and federal governments from requiring citizens to participate in prayer.

"There is overwhelming public support for restoring voluntary prayer to our public schools," E. E. McAteer of the Religious Roundtable said, urging Congress to undo court decisions that declare "God unwelcome in our classrooms."

Saying that opponents of the amendment "are generally those who favor abortion, homosexual rights and the busing of our schoolchildren," Mc-Ateer blamed the abolition of school prayer for "discipline problems, moral problems."

Supporters argued that the amendment would not impose religion on students. On different days, said Robert P. Dugan Jr. of the National Association of Evangelicals, "You'd have a Jewish student praying to the God of Abraham, Isaac and Jacob, you'd have a Roman Catholic student praying in the name of the Father, the Son and the Holy Ghost, you'd have an evangelical student praying to Our Lord and Savior Jesus Christ."

Dugan urged expanding the amendment to allow religious instruction, Bible reading, and religious clubs in schools as well as prayer.

Rabbi Seymour Siegel of the American Jewish Forum, Judiciary Committee Chairman Strom Thurmond (R-S.C.), Sen. Jesse Helms (R-N.C.) and Rep. Thomas N. Kindness (R-Ohio) also spoke out strongly in favor of the amendment.

"It does not impose prayer on anyone," Helms said. "It does not force any child to participate or even listen to prayer."

But Sen. Howard M. Metzenbaum (D-Ohio) charged that the amendment would "do violence to the time-honored recognition of the separation between church and state."

"It's very easy to wave the flag, and it's also very easy to be moralistic and emphasize religiosity," Metzenbaum said. "You don't create morality by having prayer in schools," he added.

Nathan Z. Dershowitz, speaking for the American Jewish Congress and 10 other Jewish organizations, criticized proponents for creating a "delusion of voluntariness" about the amendment.

"To a child in a classroom, no part of the school routine is voluntary," Dershowitz said. "It cannot be made so by the cruel device of telling them that they are allowed to brand themselves as pariahs by leaving the classroom, or by staying there and remaining conspicuously silent."

Representatives of the Southern Baptist Convention and the Lutheran Council also spoke against the amendment.

"The home, the church and the synagogue are the proper place" for prayer, said the Rev. Charles V. Bergstrom of the Lutheran Council. "Mechanical recitation of prayer in public school denigrates these true religious experiences."

To become part of the Constitution, the amendment must pass both houses of Congress by two-thirds votes and be ratified by three-fourths of the states. It is unlikely, however, that Congress will have time to act on the measure this year.