In which setting do students receive language assistance or content instruction exclusively in a class of ELLs?

The correct choice is a scheduled class period because this setting is specifically designed to provide focused language assistance or content instruction exclusively for English Language Learners (ELLs). In a scheduled class period, the curriculum is tailored to meet the unique linguistic and academic needs of students who are still acquiring proficiency in English, allowing for a concentrated learning environment that does not mix in native English speakers.

This dedicated structure enables teachers to implement targeted strategies and activities that enhance both language acquisition and content understanding. Students benefit from this arrangement as they can engage with peers who are facing similar challenges and can practice their language skills in a supportive atmosphere.

In contrast, other settings like a cluster center or resource center/lab may offer broader services that include mainstream students or might not focus solely on content instruction for ELLs. The push-in model involves ELL support within regular classrooms but doesn't provide exclusive content instruction separate from other students, which can dilute the focus on language acquisition for ELLs specifically. Thus, the scheduled class period stands out as the most effective approach for delivering concentrated support to ELLs.