This study draws on teacher perception data gathered from 65 secondary school modern languages (L2) teachers in South-East England. Data were collected via four iterations of an online questionnaire and follow-up interviews with six heads of department. This paper reports respondents' perceived strengths and development needs in relation to their classroom practice, including: L2 teachers' sense of self-efficacy for classroom teaching and the stability of this self-assessment over the course of an academic year; the extent to which teachers felt that their classroom practices aligned with research-informed understandings about how languages are learned; teachers' self-identified priorities for further development; and their reasons for these choices. The L2 teachers in this study reported generally strong self-efficacy scores for teaching, although scores for self-efficacy in fostering pupil engagement tended to be lower. A gap was found between teachers' endorsement of research-informed language teaching principles and their enactment of these principles in their classrooms. Many teachers reported that they would value support in developing their pupils' spoken use of the L2. Teachers highlighted spontaneity and fluency as the key speaking skills in need of development, and these priorities were highlighted by teachers at all schools and at all stages of their career.