ST. LOUIS -- Some charter schools in St. Louis are worried their increased popularity could make it difficult to stay accessible to low-income students.

City Garden Montessori, Lafayette Preparatory Academy and The Biome are working on creating income-integration programs specifically for charter schools, The St. Louis Post-Dispatch reports.

The Missouri Charter Public School Association also is helping draft legislation that would allow charter schools to set aside a percentage of enrollment spots specifically for low-income students.

State laws prohibit charter schools from admitting students based on factors such as race, income or qualifications such as grades.

The most charter schools can do is target low-income families through recruitment efforts.

Officials at City Garden and Lafayette said because of neighborhood construction and growing academic success, more affluent white families are enrolling their children, while low-income minority students are being edged out.

Officials said those charter schools always were intended to be diverse alternatives to St. Louis Public Schools.

"We expect kids to grow up and be prepared to participate in a world that's becoming more diverse," said Bill Kent, president and CEO of The Biome. "Yet in many cases, when kids come from low-income communities, we often educate them in isolation."

When demand exceeds space, the three charter schools use random lotteries to admit students.

The application deadlines, often in February, frequently end up favoring wealthier families.

Lafayette Preparatory Academy executive director Susan Marino said poorer families are less likely to be able to plan so far ahead for those application deadlines when there are more immediate concerns, such as paying bills or making rent.