Researchers often use free or reduced-price lunch (FRPL) enrollment figures as a proxy for poverty at the school level, because Census poverty data (which is used at the state and district level) is not available disaggregated below the school district level and is not collected annually. Accordingly, annual FRPL data are regularly used within school districts to determine a school’s eligibility for Title I funds. They are also used as a proxy for low-income status when determining whether a subgroup of needy students is making Adequate Yearly Progress (AYP) under No Child Left Behind.
While FRPL data is generally a reliable poverty indicator in the elementary grades, it is less so in the high school grades. Because free and reduced-price lunch is an opt-in program at the majority of schools, researchers believe that high school students are greatly under-represented in school lunch program enrollment. High school students may refuse to enroll in FRPL due to a perceived stigma attached to the program. In part because FRPL participation is an unreliable proxy for poverty at the high school level, high schools receive disproportionately lower levels of No Child Left Behind funding.