student from an unaffiliated lower-level school
Used in educational contexts to refer to a student who enters a school (e.g., a high school or university) from an external institution, rather than from an affiliated feeder school. Often contrasted with 内部生 (internal student).
At this high school, the ratio of internal students to external students is about half and half.
To enroll as an external student, you need to take the general entrance exam.
Compound of 外部 (outside, external) and 生 (student). The exact historical derivation is uncertain, but the term follows a common pattern for distinguishing internal and external students in Japanese educational systems.