Second language acquisition (SLA) is the process of learning a language after a person's first, or native, language is already in place. In schools, the term is used most often for English learners (ELs): students who speak another language at home and are still developing the English they need for school. Learning a second language takes years, and it is normal for English learners to make mistakes, go through a quiet period, and read below grade level for a while. The central question in special education is whether a student's struggles come from learning English or from a disability.
How second language acquisition works
SLA is also the name of a research field within applied linguistics. Researchers call the first language the L1 and the new language, or target language, the L2. They study why some learners reach near-native proficiency and others do not. Well-known ideas include Krashen's input hypothesis, the critical period hypothesis (the debated idea that younger learners more easily reach native-like pronunciation), and the role of motivation and individual differences. For English learners in U.S. schools, second language learning usually happens through immersion in English-language classrooms, not by studying English as a foreign language for an hour a day.
Children acquire a new language much like they learned their first language: by hearing it used in meaningful ways and by practicing it with others. Linguist Stephen Krashen described this as comprehensible input, meaning language the learner can mostly understand with some help. Learners also bring what they know from their first language. Skills such as knowing how stories work, understanding that print carries meaning, and background knowledge can transfer to the new language.
Along the way, learners use an in-between version of the language, sometimes called interlanguage. They may apply grammar rules too broadly ("goed" instead of "went"), use first-language sounds or word order, or switch between languages in one sentence (code-switching). These are normal signs of language learning, not signs of a disorder.
Stages of second language acquisition
Many teachers use a five-stage model based on the work of Krashen and Tracy Terrell. The stages are general and overlap:
- Preproduction (silent period): the learner listens and understands some words but speaks very little.
- Early production: the learner uses one- or two-word answers and short phrases.
- Speech emergence: the learner speaks in simple sentences, asks simple questions, and makes many errors.
- Intermediate fluency: the learner uses longer, more complex sentences and begins to use English for academic work.
- Advanced fluency: the learner is close to native-like in most settings, though academic language may still be developing.
BICS and CALP
Researcher Jim Cummins described two kinds of language proficiency that help explain why an English learner can seem fluent but still struggle in class:
- BICS (Basic Interpersonal Communicative Skills) is everyday social language used on the playground, at lunch, and in conversation. It is supported by context, such as gestures and facial expressions. Cummins estimated that BICS often develops within about one to three years.
- CALP (Cognitive Academic Language Proficiency) is the academic language needed to read textbooks, write essays, understand word problems, and explain ideas in science or history. It is more abstract and has less context. Cummins estimated that CALP often takes about five to seven years or more to reach grade-level norms.
The gap between BICS and CALP matters. A student who chats easily with friends may still not understand academic vocabulary in a test or lesson. Evaluators who see only social fluency may wrongly assume a disability.
Language difference vs. disability
This is the core question when an English learner is referred for a special education evaluation. Many behaviors of normal second language learning look like signs of a learning disability or language disorder: trouble following directions, limited vocabulary, weak reading comprehension, grammar errors, or a quiet, withdrawn manner in class.
Some general guidelines help teams sort out a language difference from a disability:
- Look at the first language. A true disability usually shows up in both languages. If a child has strong skills in the home language but struggles only in English, the cause is more likely second language learning.
- Compare with true peers. Compare the student to other English learners with a similar language background, time in the U.S., and schooling, not only to native English speakers.
- Check the instruction. Has the student had appropriate English language development instruction and good core teaching? Data from MTSS or RTI can show how the student responds to targeted support.
- Consider other factors. Interrupted schooling, trauma, hearing or vision problems, and cultural differences can all affect learning.
- Use a team. Include staff with expertise in English language development and, when possible, a bilingual evaluator or speech-language pathologist.
Under IDEA, a child may not be found eligible for special education if the determining factor is limited English proficiency (34 CFR 300.306(b)). At the same time, being an English learner is never a reason to delay an evaluation when a disability is suspected. Schools' Child Find duty applies to English learners too.
IDEA requirements for evaluating English learners
The Individuals with Disabilities Education Act includes specific protections for students whose native language is not English. Under 34 CFR 300.304(c)(1), assessments and other evaluation materials must:
- be selected and administered so they do not discriminate on a racial or cultural basis;
- be provided and administered in the child's native language or other mode of communication, and in the form most likely to give accurate information on what the child knows and can do academically, developmentally, and functionally, unless it is clearly not feasible to do so;
- be used for the purposes for which they are valid and reliable, and be given by trained and knowledgeable personnel.
In practice, this can mean testing in the home language, using bilingual evaluators, using nonverbal measures, and gathering information from parents, teachers, and observations. Parents who disagree with the school's evaluation can ask for an independent educational evaluation.
When the IEP team writes the plan, IDEA also requires it to consider the language needs of a child with limited English proficiency as those needs relate to the IEP (34 CFR 300.324(a)(2)(ii)).
Over-identification and under-identification
English learners can be misidentified in both directions. Some are placed in special education when their difficulties really come from learning English (over-identification). Others with real disabilities are not identified, or are identified late, because schools wait for English to improve first (under-identification). Patterns differ by age, state, and district, and both mistakes harm students.
Dual services: English language support and an IEP
An English learner who qualifies for special education is entitled to both. According to joint guidance from the U.S. Department of Education and the Department of Justice (2015), schools must provide English learners with disabilities with both language assistance services and the special education and related services they need under IDEA or Section 504. A school may not deny one because the student receives the other.
In practice, EL teachers and special education staff should plan together. IEP goals can be written with the student's English proficiency level in mind, and supports such as visuals, bilingual glossaries, or extra processing time may be listed as accommodations. Students with disabilities also take the annual English language proficiency assessment, with accommodations or an alternate assessment when appropriate.
Interpreters at IEP meetings and parent rights
Parents of English learners have the same rights as all parents in special education. IDEA requires the school to take whatever action is necessary to make sure parents understand the proceedings of the IEP meeting, including arranging for an interpreter for parents whose native language is not English (34 CFR 300.322(e)). Notices such as prior written notice and the procedural safeguards notice must generally be provided in the parent's native language, unless it is clearly not feasible. Schools should use trained interpreters, not the student or siblings.
Frequently asked questions about second language acquisition
What are the 5 stages of second language acquisition?
A common model lists preproduction (the silent period), early production, speech emergence, intermediate fluency, and advanced fluency.
What is the difference between BICS and CALP?
BICS is everyday social language and often develops within a few years. CALP is academic language used for learning and usually takes much longer, often five to seven years or more.
Can an English learner be evaluated for special education?
Yes. If a disability is suspected, the school should evaluate, using tests in the child's native language when feasible. Schools should not wait for a student to become fluent in English first.
Can a student receive both EL services and special education?
Yes. English learners with disabilities are entitled to both language assistance and special education services at the same time.
Do parents have a right to an interpreter at IEP meetings?
Yes. Schools must take the steps needed so parents understand the meeting, including providing an interpreter for parents whose native language is not English.
