State and local educational agencies, as well as schools, are accountable for making sure limited English proficient students make gains in both English language proficiency and academic content knowledge, as measured by annual academic assessments. The state is also required to provide an annual assessment of limited English proficient students in listening, speaking, reading, writing, and comprehension in English.

No Child Left Behind (full text)
U.S. Department of Education's official ESEA Web site; includes NCLB links

Executive Order 13166: Improving Access to Services for Persons With Limited English Proficiency (2000)

Federally conducted and federally assisted programs “must take reasonable steps to ensure meaningful access to their programs and activities by LEP persons,” according to the guidelines set forth by the Department of Justice.

https://www.justice.gov/crt/executive-order-13166 (full text)

Office for Civil Rights - Enforcement Policy of 1991

This document clarifies enforcement points of an EL program:
1) EL teachers must be adequately trained and be evaluated by someone who is familiar with EL teaching methods.
2) Exit criteria for students in the program should be based on objective standards.
3) Schools may not have “no double service” policies. Students who have a need can have both EL services and special education services.
4) EL students cannot be categorically excluded from special programs, such as gifted/talented education.
5) All language minority students must be assessed for fluency.
6) Parents are to be provided with information related to school in a language that they understand.
7) EL students are to receive instruction from qualified staff.

http://www.ed.gov/about/offices/list/ocr/docs/lau1991.html

Congress - Civil Rights Restoration (1988)

If any part of an institution or agency receives federal funding, the entire entity is prohibited against discriminatory practices. If any part of the organization violates civil rights laws, federal funding may be withdrawn.

Fifth Circuit Court - Castañeda v. Pickard (1981)

The adequacy of a district's EL program will be evaluated by a three-part test:
1) Is the program based on sound educational theory or is it considered by experts in the field to be a legitimate strategy?
2) Are the programs, practices, and resources available to implement the strategy effectively?
3) Does the school district evaluate and adjust its EL programming to ensure the effectiveness of its strategy?

Fifth Circuit Court - Castañeda v. Pickard (1981) (full text)

Supreme Court - Plyler v. Doe (1981)

Under the Fourteenth Amendment, all students have the right to free public education and must be appropriately served, regardless of their status as citizens, documented immigrants, or undocumented immigrants.  It is not the role of school systems to enforce immigration law. Furthermore, it is not  an acceptable argument to deny educational services to undocumented students because of the burden it may place on school systems.

Supreme Court - Plyler v. Doe (1981) (full text)

Supreme Court - Lau v. Nichols (1974)

The Supreme Court ruled that districts must help limited-English proficient students overcome educational barriers through equitable (not equal) access to facilities, textbooks, teachers, and curriculum. 

Supreme Court - Lau v. Nichols (1974) (summary)

Equal Education Opportunities Act of 1974

States may not deny equal educational opportunities to students due to race, color, sex, or national origin. Educational agencies must take appropriate action to ensure that language barriers do not impede students' participation in instructional programs.

Equal Education Opportunities Act of 1974 (summary)

U.S. Department of Health, Education, and Welfare - May 25 Memorandum (1970)

This document clarifies a school district’s responsibility towards English learners:  “where inability to speak and understand the English language excludes national origin minority group children from effective participation in the educational program offered by a school district, the district must take affirmative steps to rectify the language deficiency in order to open the instructional program to the students.”

http://www2.ed.gov/about/offices/list/ocr/docs/lau1970.html

Title VII of the Elementary and Secondary Education Act of 1968
(Bilingual Education Act)

The Bilingual Education Act authorizes funding to support educational agencies who serve students with limited English proficiency. This funding may also be used to provide professional development and research opportunities related to serving English learners. The Act was reauthorized and restructured in 1994 as part of the “Improving America’s Schools Act.” In 2001, Title VII was replaced in the re-authorization of ESEA and the No Child Left Behind Act, and is now Title III “Language Instruction for Limited English Proficient and Immigrant Students.”

Title VI of the Civil Rights Act of 1964

Title VI prohibits discrimination by recipients of federal funds against anyone on the grounds of national origin, color, or race. This has been interpreted to include the prohibition of denial of equal access to education because of limited proficiency in English.

Title VI of the Civil Rights Act of 1964 (full text)