English as a second language; ESL; TESOL ; Bilingual method ; Instruction (medium of) ; Medium of instruction ; Kode (Kommunikationsforschung) ; Speech codes theory; Accommodation theory (communication research) ; Code (communication research) ; Classroom communication; Instructional communication ; Foreign language teaching policy ; Alternation (biling.) ; Language shift (biling.) ; Sprachwechsel (biling.) ; English ; Taiwanesisch; Taiwanese