noun
supplementary reader (in foreign language class)
Wasei-eigo term for a graded reader or extra reading material used alongside a main textbook in language classrooms.
wasei-eigo (Japanese-coined English), from side reader
英語の授業では、教科書の他にサイドリーダーを使っています。
In English class, we use a supplementary reader in addition to the textbook.
Variant with a middle dot, sometimes seen in printed materials.
副読本 is a more general Japanese term for a supplementary reader, not limited to foreign language learning.
Wasei-eigo from English 'side' + 'reader', referring to a supplementary reading book used in language education.