Prince George's is such a vast, varied county that generalizations often fail to do it justice. That is especially true of its school system.

Is it urban? Yes. Suburban? Yes. Affluent? Middle class? Poor? Yes, threefold. Is it on the rise or under-achieving? Arguably, both.

Despite its national prominence as a majority-black county of growing wealth, Prince George's often suffers in educational comparisons with Maryland's other 22 counties.

"It's frustrating that we are in many ways very different, and usually we are treated as though everyone is the same," said schools spokesman John White.

In some ways, such comparisons are predictable when federal law literally decrees that no child may be left behind.

In size, the 136,000-student Prince George's system ranks second only to 139,000-student Montgomery. To assess the Prince George's schools, it helps to break the system into parts. School officials have done so by creating five regions, each overseen by an assistant superintendent. But those regions are somewhat difficult for residents to visualize.

For the sake of analysis, here's one way to divvy the system into four parts, using two widely known roads: the Capital Beltway and Central Avenue.

North of Central Avenue and inside the Beltway lies one sector, anchored by the University of Maryland and older towns such as Bladensburg, Hyattsville, Mount Rainier and Cheverly. North of Central and outside the Beltway is a second sector that includes Bowie, Laurel and the newer community of Mitchellville.

South of Central and inside the Beltway, a third sector includes Suitland, District Heights, Forestville and Capitol Heights. And a fourth sector, south of Central and outside the Beltway, sprawls south and east around Andrews Air Force Base, spanning Upper Marlboro, Brandywine, Clinton and Fort Washington.

Here are findings from a Washington Post analysis of school enrollment and ratings in these four sectors: First, all are large. The smallest -- the third sector, with about 23,000 students -- is bigger than 14 county systems and nearly as large as 26,000-student Charles County. The largest -- the second sector -- is on par with 40,000-student Harford County and 39,000-student Frederick County.

Second, the two sectors inside the Beltway, combined, account for 70 percent of the county schools that failed this year to make adequate yearly progress under preliminary state ratings released last month. Test scores in these areas are weighed down, experts say, by lower income levels, which hinder student achievement.

That is not to say that all schools inside the Beltway are floundering -- far from it. One of the highest performers in the county, Glenarden Woods Elementary, is inside the Beltway. Pockets of affluence inside the Beltway drive scores higher in some schools. Many of the inside-the-Beltway schools that failed to make the state benchmark are nonetheless improving.

But it seems clear that the county system will not rise to the level of its neighbors on test scores unless the inner-Beltway schools make substantial gains for several years.

Here are slices of data found in the Post analysis. (High school achievement ratings for 2005 were not available.)

* North of Central, inside the Beltway: 63 schools with 39,145 students, using state data as of September 2004. (Bladensburg High, temporarily in Bowie in the past few years, was counted in this sector.) Percent of county enrollment: 29.

Number of elementary and middle schools that failed to make adequate progress in 2005, using preliminary state data released June 20: 28. Percent of county total: 35. On preliminary state watch list calling for improvement: 21 elementary and middle schools, three of them required to restructure.

* North of Central, outside the Beltway: 47 schools with 39,927 students. Percent of total enrollment: 29.

Number of elementary and middle schools that failed, preliminarily, to make adequate progress: 10. Percent of county total: 12.5. On preliminary watch list: seven schools, one of them required to restructure.

* South of Central, inside the Beltway: 40 schools with 23,443 students. Percent of total enrollment: 17.

Number of elementary and middle schools that failed, preliminarily, to make adequate progress: 28. Percent of county total: 35. On preliminary state watch list: 18 schools, three of them required to restructure.

* South of Central, outside the Beltway: 50 schools with 33,580 students. Percent of total enrollment: 25.

Number of elementary and middle schools that failed, preliminarily, to make adequate progress: 14. Percent of county total: 17.5. On preliminary state watch list: 12 schools, two of them required to restructure.

Despite evident disparities, the school system says it is seeking to deliver the same quality of education to every school.

"There shouldn't be haves and have-nots," White said.