Higher-education groups said yesterday they were unappeased by last week's budget compromise between the Reagan administration and Senate Republican leaders that would cut college student aid by $2.6 billion over the next three years.

The target of most of the criticism is a proposal to use $8,000 as the assumed annual cost of a college education when deciding the amount of federal money that would be available to a student.

Under the compromise, the government would subtract from the $8,000 an amount that the student's family would be expected to contribute, based on the family's size and income.

The remainder would be the amount of federal money available to the student.

That $8,000 figure is far less than the cost of many private universities and colleges.

Education groups said yesterday that the limit is unfair to those schools, and could amount to a deliberate effort to drive a wedge between public and private colleges in the battle for federal student aid dollars.

"We think it's pretty outrageous," said Charles Saunders, vice president for governmental relations at the American Council on Education.

"It seems to just kiss off the neediest students and tells them don't even bother trying to attend one of the more-expensive private schools," Saunders said.

"We think it's wrong, and a malicious kind of approach to splitting the higher-education community."

In the 1983-84 academic year, more than 700 of the 1,500 member schools of the National Association of Independent Colleges and Universities had total student costs exceeding $8,000, according to figures compiled by the group and released yesterday.

Bill McNamara, a spokesman for the group, said that $10,848 was the average annual cost of students attending NAICU schools.

Other university spokesmen yesterday called the compromise package no better than the initial Reagan administration proposal.

"We don't consider it much of a compromise," said Richard Jerue, vice president for governmental relations for the American Association of State Colleges and Universities. "Our feeling is that this is still a major cutback in higher-education funding."

Initially the administration had proposed setting a total $4,000-a-year "mega-cap" on most forms of federal aid to college students: guaranteed loans, work-study money, and low-income Pell grants.

That proposal came under sharp bipartisan criticism on Capitol Hill.

Some congressional staffers, who were still trying to piece together details of the compromise yesterday, said some senators may have thought that the new $8,000 figure meant that the "mega-cap" would be doubled.

The budget package, which President Reagan endorsed last Thursday, would also:

* Set a new cap denying guaranteed student loans to families with incomes of more than $60,000.

The limit originally was put at $32,500, but that figure, too, came under heavy criticism in Congress.

* Tighten the rules under which students could declare themselves independent of their parents for the purpose of obtaining more student aid.

Now, students must be independent for at least one year before attending school.

The compromise proposes extending this time to two years.

* Reduce from 4 percent to 3.7 percent the amount of the government's subsidy on guaranteed student loans.

Now, under the program, the student pays 8 percent of the interest rate and the government pays 4 percent, in addition to guaranteeing that the loans will be repaid.