CALEXICO, CALIF. — A SOCIOECONOMIC gulf apart, Claudia Ramirez, a Mexican farmworker's daughter, and Ed Magrew, a wealthy farmer, share common ground in the Imperial Valley, where the striving third world meets the efficiency and productivity of the first.The Imperial Valley is supposed to be the poorest place in California, but it doesn't feel that way. To be sure, with a 19 percent unemployment rate and a $10,000 median income, "there is an underclass," says Susan Giller, managing editor of the Imperial Valley Press. "But for all the poverty that is here, it doesn't look poor." Ms. Ramirez, whose parents support five children with welfare and disability benefits her father gets for an injured back, has found remarkable success here. Shy behind her braces and braids, Ms. Ramirez is the first in her family to progress beyond elementary school. She moved here from Mexicali, Mexico, just across the border, four years ago, learned English, and graduated second in her Calexico High School class last month. Headed to the University of California, San Diego, on a scholarship, she says her education in Calexico has guaranteed what Mexico could not: a career as a college math professor. Ten miles north in Holtville, Mr. Magrew is a tanned and articulate asparagus and hay exporter who has converted some of his land into a recreational vehicle park, golf course, and jet-ski lake in an effort to capture a share of the expected growth in tourism and residents stemming from efforts by the county to diversify its farm economy. Though many of his colleagues bristle at the looming free-trade agreement with Mexico, Mr. Magrew brims with excitement over the race to capture the Mexican market. "If a person wants to be on the cutting edge [of agriculture], this is it," he says. "We can control our environment. I can pick up the phone and order water for tomorrow. It's frost-free year round [here], the soil is productive, we've got the Pacific Rim [market], and now we're about to have Mexico [under the Free Trade Act] and 90 million potential customers." Reynaldo Ayala, director of the Institute for Border Studies at San Diego State University's Imperial Valley campus, sees the valley in other terms. "It is the poorest county, but at the same time one of the richest in agricultural production in the country," Mr. Ayala says. "Those with economic power to produce the agricultural riches exist next to poor labor...." The poor Mexican labor force is a majority of the population of both sides of the Imperial-Mexicali Valley. Indeed, sometimes as much as 70 percent of California state unemployment benefits distributed in Imperial County go to residents of Mexico. "This is not a place of depression. This is a starting-off point for a better life," observes Roberto Moreno, assistant superintendent of the Calexico Unified School District. The poor immigrants, he says, are "coming from worse places and they're really optimi stic." While many residents here may have a low standard of living compared with other parts of the United States, certain aspects of life here, like the schools, make the standards of living higher than across the Mexican border. Calexico High School, a generation ago on the edge of losing its accreditation, has won national recognition for its low Hispanic dropout rate. Overall, the state's dropout rate for Hispanics is 29.2 percent, and 14.4 percent for Anglos. But the high school dropout rate is just 11 percent in the Calexico school system, where 98 percent of the students are Hispanic, 80 percent begin school not understanding English, and 85 percent of the students come from low-income families. "The entire environment here is supportive," says Mr. Moreno. It is much easier to get crucial support from poor immigrant parents when the community, its leaders, schoolteachers, and staff are mainly Hispanic and Spanish-speaking, he says. The US-Mexico border cuts through what would be one city - Calexico, Calif., and Mexicali, Mexico. But mentally, for valley residents, the border is drawn somewhere north of Calexico, says Al Velasco, a San Diego social worker who grew up in Calexico and still owns his family home here. "We were a suburb of Mexicali; you'd go there for haircuts and to buy clothing," he says. "We saw El Centro [the county seat] as the seat of power of the rich Anglo farmer, where shopping centers and movie theaters were." While thousands of people share family, business, social, and language ties across the border, the international line is still a huge barrier in many ways. For example, a former Mexicali mayor could not name the current mayor of Calexico; similarly, a prominent California-side businessman could not name the mayor of Mexicali, a city of 1 million just over the border. Then there are many more people on both sides of the border who rarely if ever cross the line: Those in Mexico who cannot because they don't have the immigration papers to do it, and those of northern Imperial Valley towns who won't because they see the mangled border fence as symbolic of the forbidden edge of another world. Though northern valley communities see themselves as independent of the Mexican economy, and search to diversify their agricultural economy, it is "scary" how dependent on Mexicali's spending power they are, says one businessman. He says the aggressive retailer WalMart chose El Centro as one of its first locations in California for one reason: its proximity to the big Mexicali market. Calexico is totally dependent on Mexicali consumers, says Mark Holloway, president of the Calexico Chamber of Commerce. The Mexican population is so important to his 75-year-old family-owned department store that he will not employ sales clerks who don't speak Spanish. Indeed, Mr. Holloway's parents felt it was crucial to the store's future that as a child he attend Mexicali schools to ensure his understanding of Hispanic language and culture.