Research indicates English learners perform best when teachers are required to have state certification to teach English as a Second Language (ESL), English to Speakers of Other Languages (ESOL), bilingual or other type. At least 39 states provide for training, professional development, teaching standards, certification or endorsements for EL-specific teachers in statute or regulation. In some states, certification and endorsements are required. In other states, endorsements and certification are available, but it is unclear whether it is required. [View the full "50-State Comparison: English Learner Policies" here: https://www.ecs.org/50-state-comparison-english-learner-policies.]