This digest defines the term "extended school year" (ESY) and notes the issues of regression and recoupment which have led to development of ESY services for students with disabilities. The digest then provides answers to the following questions: (1) When is ESY needed? (2) How is eligibility for ESY determined? (3) What are some factors that could mandate a need for ESY? (4) What other factors may be considered in offering an ESY program? and (5) What types of delivery models are available? Includes 13 references. (JDD)