THE 10-MONTH-OLD school board in Prince George's County -- judiciously chosen from a rich pool of knowledgeable talent -- has in turn made its first and most important decision since taking office. By an 8 to 1 vote, it has selected Andre J. Hornsby, a former Yonkers, N.Y., school superintendent, to be chief executive of the county's struggling school system. The choice has been greeted somewhat tepidly, not so much a reflection on the candidate, we suspect, as on the challenge he faces. Mr. Hornsby's greatest strength so far has been his ability to improve test scores in the two years he headed the 26,000-student Yonkers system and in a 24-school region of Houston's system, which he ran for three years before that. Whatever else he brings to the job, in Prince George's his test score will hinge on the scores of the students.

The Prince George's system has ranked second to last among Maryland's public school systems on most state and national standardized tests. Superintendent Iris T. Metts saw some encouraging improvements in her early years in office, but she was upstaged and undercut by a singularly terrible school board that had to be put out of its hyper-political misery last year. Mr. Hornsby is no stranger to conflict with boards, unions and other most-likely-to-grouse players in a school system, but the scope and layers of factional discontent in Prince George's County are extraordinary. And the enrollment is more than five times that of Yonkers.

Members of the current board have cited their firm belief that Mr. Hornsby had the most experience working with relatively large minority populations and limited resources. Though the Prince George's system is in line for an infusion of money approved by the state last year, Mr. Hornsby knows enough already not to count on it. He says his administration will have to shift and consolidate some resources -- and he begins with a sensible approach: Mr. Hornsby says he will ask people to "define their work for me, especially the people at the top." Though he will not take office formally until July 1, he will join in the budget considerations before that. Otherwise, he says, any budget changes would have to wait until the following academic year.

Mr. Hornsby says he also plans a review of the county's magnet school program, noting that in Houston he found too much focus on magnets at the expense of the rest of the system. Noting the school system's serious literacy problem, he says he will consider requiring changes in the county's teacher instruction program to align it better with specific shortcomings of individual students. Mr. Hornsby is well aware that Prince George's has too many inexperienced teachers who, once trained, tend to leave for other systems. He talks about better training and support as incentives for teachers to stay.

"There's nothing wrong with the kids," Mr. Hornsby says. "We've got to realign instruction. . . . Today's kids have got to know things faster. The curriculum is more compressed. We must get specific about what kids don't know."

We'll see. The doubters should give him a fair test, allowing him the time and leeway to make changes that he believes could move the system -- and students -- up the ladder.