彼(かれ)等(ら) kareraは wa授(じゅ)業(ぎょう)中(ちゅう) jugyouchuuだ da。 They're in class. Literal They [topic-は] in-class [copula-だ]. 授業中 uses the suffix ~中 (ちゅう, 'during'): 'in the middle of class.' school~中 (during/in the middle of)
彼(かれ)等(ら) kareraは wa授(じゅ)業(ぎょう)中(ちゅう) jugyouchuuだ da。 They're in class. Literal They [topic-は] in-class [copula-だ]. 授業中 uses the suffix ~中 (ちゅう, 'during'): 'in the middle of class.' school~中 (during/in the middle of)