When does a school district's decision to educate a child with disabilities outside the regular classroom violate the IDEA's mainstreaming mandate?

QUESTION PRESENTED The Individuals with Disabilities Education Act (IDEA), 20 U.S.C. § 1400 et seqg., conditions federal funding on compliance with several requirements, including a directive that students with disabilities be educated, “[t]o the maximum extent appropriate,” “in regular classes with the use of supplementary aids and services.” § 1412(a)(5)(A). As this Court has recognized, that statutory mandate reflects Congress’ “mainstreaming’ preference,” Bd. of Educ. v. Rowley, 458 U.S. 176, 202-03 (1982)—i.e., that “children with disabilities receive education in the regular classroom ‘whenever possible.” Endrew F. ex rel. Joseph F. v. Douglas Cty. Sch. Dist. RE-1, 137 S. Ct. 988, 999 (2017) (quoting Rowley, 458 U.S. at 202). The courts of appeals have divided on how to interpret this mainstreaming mandate. The First Circuit permits a school district to remove a child with a disability from regular classes so long as the district weighs the costs and benefits of different placement options and picks one educators find appropriate. The Second, Third, Fifth, Tenth, and Eleventh Circuits track the IDEA’s text by requiring mainstreaming whenever a child’s education can be achieved satisfactorily in regular classes with supplementary aids and services and program modifications. The Fourth, Sixth, and Eighth Circuits apply a test that starts from the assumption that segregated special education classes are superior. And the Seventh and Ninth Circuits have taken still different approaches. The question presented is: When does a school district’s decision to educate a child with disabilities outside the regular classroom violate the IDEA’s mainstreaming mandate?