Federal education programs for disadvantaged children often disrupt the school day so severely that the students involved become confused and lose out on regular course work, according to a nationwide study by the Rand Corp. released yesterday.

The year-long study, conducted for the Department of Education, said many students in the special programs are pulled out of their regular classes for tutoring or remedial work two or three times a day.

In some cases, where many children are in several different federal programs, the regular classroom teacher has the total class for only an hour and a half a day, the study said, drastically reducing the time available for the state-mandated curriculum.

Researchers Jackie Kimbrough and Paul Hill said they found some migrant Hispanic children in fifth grade who never had classes in science or social studies because they spent nearly all their school time in different and sometimes conflicting remedial programs in reading and math.

"There may be some validity to the notion that students need massive and multiple 'doses' of supplementary instruction in their areas of deficiency," said Kimbrough and Hill, "but excessive pullouts are bound to disrupt the student's regular education."

Hill said in many cases children "are taught different skills in the same subject, such as arithmetic, in different sequences. The kids get confused."

The Rand Corp., which conducted the study, is a nonprofit research organization based in Santa Monica, Calif. Hill said the study was ordered by the Carter administration about six months before it left office.

Since Reagan officials took over in January, they have frequently attacked federal education rules and sought sharp cutbacks in federal aid.

Yesterday Paul Smith, research director of the Children's Defense Fund, which strongly supports the federal programs, said the study contains "absolutely nothing new" and simply amplifies "the complaints of public school educators who feel their burdens are very great."

"The bottom line has to be: Did the programs work?" Smith continued. He said evidence from the National Assessment of Educational Progress indicates that they have been successful.

In an interview Hill agreed that many federal programs are "valuable." But he added, "That doesn't mean they aren't a problem too and can't be made much better." He said local schools are "really burdened by the sheer number and separateness of the programs," even with changes aimed at loosening regulations voted by Congress last summer.

At present most federal aid programs are supposed to be for particular "identified" children. Even though the pullout classes are not required by regulations, the study found they are used by most school systems to simplify fiscal and program record-keeping that the government requires.

One unintended effect of the federal programs, the study said, is to put many black and Hispanic children in segregated classes for much of the day even though their schools may be under court desegregation orders.

In addition, because some state and federal requirements come with little or no money, the study said children often are assigned to programs that have funds rather than the ones they need.