The document describes the differences between CALP (Cognitive Academic Language Proficiency) and BICS (Basic Interpersonal Communication Skills) for English language learners. CALP refers to formal academic language skills needed for school success, which typically takes 5-7 years to develop. BICS are everyday social language skills, which usually develop within 6 months to 2 years after arriving in the US. The document also notes recent research finding it can take ELLs 7-10 years to academically catch up without support in their native language.