Tuition grants for Virginia students attending private colleges in the state would be increased $250 next year to $1,500, under a proposal approved yesterday by the state Council of Higher Education.

Gordon K. Davies, executive director of the council, said that as the grants increase in size, the panel should study the idea of basing at least part of the annual award on financial need in order to stretch the available dollars. A total of 13,035 students attending 27 schools received grants during the last school year.

The council, meeting at George Mason University in Fairfax County, voted to ask the General Assembly to raise the annual grant when it approves the state's two-year budget in 1988. The increase was sought by the Council of Independent Colleges in Virginia, which says the grants help less well-to-do students attend private colleges, which generally have higher tuitions than do state-run schools.

Davies told the council that once the grant reaches $1,500, "we should begin a restructuring discussion . . . to introduce need into the equation. This will be a $35 million program. That's a substantial amount of money."

The financial aid formula could be written so that middle-income families remain eligible, he said.

In North Carolina, which has a similar program, state residents are eligible for a $1,100 grant and needier students may receive an additional $400, he said. In Virginia, basing part of the grant on need could enable lower-income students to receive as much as $2,000, he said.

The state also runs a college scholarship program based on need, which last year dispensed grants averaging $734 to 5,926 students. Davies suggested the grant and scholarship programs be combined.

In other business, several council members questioned a Virginia law that requires them to grant blanket exemption from state regulation to religious colleges offering degrees only in religious subjects.

The law stems from concerns about separation of church and state, but some council members said it could leave the impression that the state has approved the colleges' degree offerings.

"It seems to me when we're conferring degrees that we ought to have more say over what's happening," said council member Hugh L. Patterson of Norfolk. Patterson and other members asked staff members to brief them on their options at a future meeting.

Exemptions have been granted to 18 religious colleges in Virginia, seven of them in Northern Virginia. Yesterday's discussion was prompted by the council's vote to grant an exemption to International Christian University in Chesapeake.

Institutions run by churches but offering liberal arts degrees, such as the Rev. Jerry Falwell's Liberty University in Lynchburg and the Rev. Marion G. (Pat) Robertson's CBN University in Virginia Beach, are not eligible for exemptions.