The Maryland Board of Education today closed an administrative loophole that parents claimed allowed them to teach their children at home without state regulation because the instruction qualified as a Christian school.

The action highlights a lingering dispute between the state Department of Education and fundamentalist Christian educators, who contend that parents teaching church-related curriculum at home constitute "satellite" schools and should be exempt from government control.

In other action at its monthly meeting here, the board tentatively approved a requirement that new teachers pass a standardized test before they are certified, a provision that has stirred debate across the country as it is adopted by an increasing number of states. The board will take final action on that requirement after a public hearing this fall.

On the issue of home instruction, the board specified that parents teaching one or two of their children at home do not constitute a "school."

Some parents teaching church curriculum at home have argued that they are satellite schools and should be exempted from any state control, as are bona fide church-affiliated campus schools.

Instead, the board said today, these families must meet home-instruction regulations, which mandate certain academic standards and approval from local school authorities.

The new definition was made "just to change a loophole of parents trying to evade the home-instruction bylaw," said Ellen Heller, deputy state attorney general for education.

She repeated assertions by the board that the revisions were not an effort to thwart home teaching.

"There is a right to teach your children at home in Maryland. No one is trying to take that away."

The board acted despite about 400 written protests from persons who argued that the change would allow unlawful government interference into their church activities. But the revision was less stringent than an earlier proposal that would have required at least seven students to be receiving instruction in order to qualify as a school.

"It's certainly going to hurt the ministry of the church," said Rev. Roger L. Salomon, executive director of the Maryland Association of Christian Schools.

"We do everything we should do to guarantee a good, quality education. These home students must go to the local superintendent for permission. We feel they ought to go to the church for permission," Salomon said.

Under the revised language, at-home teaching can be considered a "school" only when there are at least two unrelated children and where at least two children are not being instructed on a daily basis by their parents.

State officials do not accept the argument that families teaching church curriculum constitute satellite schools and so should qualify for the church exemption. "If you are a parent teaching at home, you are a home-instruction situation, no matter what course of study," Heller said.

The dispute began nearly two years ago, when a Frederick pastor informed the state he was establishing satellite schools. Gary Cox, pastor of the Walkersville Christian Fellowship, said he has since helped about 50 families teach at home by supplying curriculum and other academic assistance.

The state Department of Education has informed Cox that his schools constitute home-teaching and are subject to local approval and state guidelines, which require a qualified teacher and curriculum appproved by local authorities.

Cox, who says he requires his schools to submit sample work, testing and attendance records to ensure their quality, said he will continue to negotiate with the state.

In the board's other business, the proposed teacher-testing requirement, if given final approval by the board, will mandate that teachers seeking certification after July 1988 pass four subtests of the National Teacher Examination, including a test in their area of specialization.

"Every opportunity we have, we ensure the people we hire are qualified," said board President Frederick K. Schoenbrodt.

If approved, the requirement will make Maryland one of about 25 states with teacher-testing requirements, 18 of which have gone into effect since 1982.

"I question why we need it, but I also see no harm in it," said Janice Piccinini, president of the Maryland State Teachers Association.

The proposed regulation will mean that new teachers must take the tests on a "no-fault" basis beginning next April. After July 1, 1988, new teachers must earn a passing score, which will be established by the state superintendent.