As the Howard County school board begins wrestling to reconcile its plans for services next year with the prospects of a tight budget, the county's longtime custom of paying transportation costs for students in parochial schools is expected to come under new scrutiny.

Howard County has the most extensive parochial school busing program in the Baltimore-Washington area, although 11 other jurisdictions have similar laws permitting or requiring the use of public funds to transport private school students, according to recent statistics from the Maryland Department of Education.

The 45-year-old transportation program, which costs nearly a quarter of a million dollars, has been criticized by some county residents who say that it violates the constitutional separation of church and state. School board member Karen B. Campbell, who has promised to raise the issue in the board's budget deliberations, said she opposes the program "as a matter of principle. Public tax money should not be spent on private schools."

At the same time, Del. Bob Kittleman, chairman of the Howard County legislative delegation, said the public funding is supported by a "good size constituency." Repealing the ordinance, he said, could mean the "loss of a lot of goodwill and support" for education overall.

A majority of the school board agreed with Kittleman, and noted that the busing was established after the legislature passed a bill requiring the county to provide the service. Board member Bill Manning said, "Until the legislature makes a change, we are obliged to provide a service."

Nonetheless, Kittleman said he expects county funding of parochial school busing to be questioned as the school system's funding becomes tighter.

"There may be more nibbling away" at the county's 1943 ordinance, said Kittleman, a second-term Republican who serves as the House minority whip. "It's not strong yet, but the PTAs will begin to question it more and there will some type of dialogue."

Education officials said they expect the issue to be raised today at a 7:30 p.m. public hearing on Superintendent Michael E. Hickey's proposed 1989 school budget.

School board members said parochial school busing may draw fire because of Hickey's proposed $133.7 million "hold-the-line" budget in which the $511,000 for new programs and services is the smallest amount proposed in the past four years. Of the additional $16.5 million requested for next year, 63 percent would go toward teacher pay raises, while 34 percent is earmarked to maintain existing programs and class sizes, Hickey said.

For the 1988-89 school year, school transportation officials have proposed a 3.5 percent increase, from $237,550 to $246,310, in the parochial school busing program. The money would be used to transport about 600 students to four private schools: St. Augustine School in Elkridge, St. Louis School in Clarksville, Our Lady of Perpetual Help in Illchester and Resurrection School in Ellicott City. A fifth school, Bethel Christian Academy in Savage, also has asked for bus service next fall, said Robert S. Lazarewicz, director of operations.

In Howard, transportation costs per parochial pupil are more than double the costs of regular public school students, according to county school officials. This year, the per pupil cost is expected to be $382 for each parochial student, compared to $180 for each regular public school student.

In October, the school board reviewed the parochial school busing program for possible cutbacks or elimination. However, the board decided then to leave the program intact until the county law is revised or repealed.

Howard County Council Chairman Ruth Keeton said the council has discussed revising the 1943 law several times, but formal legislation has never been introduced to accomplish that goal.

In Anne Arundel County, rapid population growth, boundary line changes and staggered opening times for public schools have decreased the number of private students transported by public school systems, said Bill Kerns, supervisor of the county's public school transportation.

Also, more private schools are providing their own bus service or contracting with independent bus companies to transport their students, county school officials said.

Parochial school busing also has waned in Montgomery, although the county sets aside extra money in the school budget for the service, said Michael Fleming, director of the school system's transportation department.

In the proposed 1989 budget, Montgomery proposes to spend $18,087, up from the current budget of $17,635, he said.

Fleming said parochial school busing has generated little opposition in Montgomery in the past 15 years.