The Charter School at Waterstone looms behind a manned guardhouse in an exclusive community in Homestead. With a palm-lined walkway leading to its cool-blue buildings, the school stands apart from the closest alternative: Campbell Drive K-8 Center, the 35-year-old traditional public school down the road.

The students are different, too.

At Waterstone, about 32 percent of students in 2010 qualified for free or reduced-price lunches, an indicator of poverty, according to data from the National Center for Education Statistics. At Campbell Drive, about two miles away, 93 percent of the students qualified.

The trend is evident across Miami-Dade County, where overall, the number of poor children enrolled in charter schools is disproportionately low compared to traditional public schools — an advantage for the charter schools, given that poverty correlates with poor academic performance. Charter schools in Miami-Dade also enroll a smaller share of black students than traditional public schools, according to federal data. In traditional public schools, one-third of children are black, compared to one-fifth of children in charter schools.

The imbalances persist despite local, state and federal rules aimed at promoting open access to charter schools and preventing discrimination. The Waterstone school, for example, is open to all Miami-Dade students under its contract with the school district, while giving preference to students who live within four miles of the school — an area that includes Campbell Drive K-8.

Charter schools, which receive public tax dollars but are run by independent boards, say they do not handpick which students they enroll. Most say they rely on random admissions lotteries.

And in Broward County, the charter school demographics more closely reflect the traditional public schools.

“Charter schools serve the neighborhood kids,” said Robert Haag, president of the Florida Consortium of Public Charter Schools, a lobbying and support organization.

In Miami-Dade, however, the charter school industry has followed a growth strategy that has amplified the disparities. Much of the growth in charter schools has been in the county’s western and southern suburbs rather than the inner city — in part because of the housing boom of the 2000s. Moreover, some schools have adopted outreach strategies that target high-achieving students and children who live in affluent neighborhoods.

Florida school districts are not required to monitor charter schools’ admissions lotteries or marketing methods, and they seldom do — even with millions of dollars in taxpayer money on the line . But in 2009, Miami-Dade school district researchers looking at enrollment patterns found that the Mater and Doral academies, two popular charter school networks managed by the same company, had admitted a disproportionately high percentage of advanced students. The findings raised the possibility “that specific students were targeted in some way,” according to the report.

The school district never pursued the numbers further, and the two school networks denied the accusations.

As charter schools expand their reach, the issue remains a topic of national debate.

“There are questions about whether these schools truly are open to serving everyone,” said Erica Frankenberg, an assistant professor at Pennsylvania State University who studies charter schools.