The Reagan administration yesterday backed away from some controversial proposals to relax the government's rules for educating handicapped children, saying the most hotly contested proposals may be held for further study.

Education Secretary Terrel H. Bell told a crowded public hearing that changes proposed Aug. 4 in rules implementing the Education for All Handicapped Children Act already had begun to generate a "quite enormous" volume of comment.

"We're not dug in and set on any specific provision," he said. "We are considering the possibility of holding for further study . . . some of the provisions that are drawing a lot of attention and concern and some of the provisions that may need considerable revision."

The proposed changes were not to have gone into effect until several months after the comment period ends in November, and their implementation is now uncertain.

The administration earlier postponed action until after the Nov. 2 elections on two other touchy proposals, one to expand child labor laws to ease employment of 14- and 15-year-olds and the other to relax enforcement of affirmative action rules for government contractors.

Stressing that the notion was "highly tentative," Bell said he might hold back the new rules in three areas of major debate:

* Parental consent. The Department of Education (DOE) wants to delete the requirement that schools obtain parents' written agreement to whatever treatment and placement is proposed for a handicapped child. The rule often has led to lengthy litigation, and Shirley Jones, DOE acting deputy director of special programs, said it should be a state concern.

But parents at the hearing expressed worry that they might lose all say in their children's future. "It's back to the closet, don't kid yourself," said Justine Maloney of Arlington, mother of an epileptic 15-year-old girl, in an interview. She wore a button that said, "Nobody's perfect."

* Deadlines. The proposals would eliminate the 30-day deadline by which a school district must evaluate a child and set up an individualized educational plan. Instead, states would have to set "reasonable" time limits and justify them to DOE.

* Placement. The law requires placement in the "least restrictive environment," as much as possible in ordinary classrooms, but proposed rules would kill the requirement that each school district provide a full range of treatment options.

Medical services such as injections would become optional, and the new rules would allow teachers to exclude students for "disruptive" behavior not directly associated with their handicaps.

Backers of the 5-year-old act call it a bill of rights for disabled youngsters. The DOE said its changes would halve paperwork and give states and localities more flexibility, while guaranteeing equal schooling for the nation's estimated 4 million handicapped children.

George Conn, commissioner of rehabilitation services, said schools forced to provide a range of treatments usually filled each program with students, whether or not the service was appropriate.

But Libby Paul, a Prince George's County mother of two handicapped children, said, "A diabetic kid could be denied an education because a school district doesn't want to provide medical care." She said she had 7,000 signatures on a petition opposing any rules changes.

The hearing, the first of 11 to be held nationwide, continues today. Comment will be accepted until Nov. 2.