Few studies have examined how teachers' oral feedback in whole-class interactions is received, perceived and used by students to enhance learning. This paper details an in-depth study of secondary teachers' and students' reflective comments on classroom oral feedback. The study examined perceptions of teachers and students in English and mathematics classroom interactions. Key findings showed that much teacher feedback was not recognised by students, and that when feedback was recognised it was often not perceived as the teacher had intended. Further, feedback in mathematics was more often recognised and perceived as intended compared to English. If feedback is not received by students, or not perceived as intended by the provider, it is unlikely that the feedback message will achieve its intended effect of supporting student learning. The study provides evidence that feedback perceptions -- and thus feedback effectiveness -- are context-dependent, subject-dependent, and individual-dependent.