The purpose of the present study is to investigate 1) the teachers' beliefs about classroom assessment in English, 2) their actual classroom practices, and 3) the extent to which their beliefs are congruent with their actual assessment practices. The participants were grade-6 English teachers in a school district from the northeastern part of Thailand. The present study was conducted using a mix-methods approach. The study consisted of two phases. Phase 1 involved the administration of a questionnaire to 97 teachers. Phase 2 was comprised of two parts: 2.1 classroom observation and stimulated recall with six teachers and 2.2 semi-structured interviews with 13 teachers. The findings revealed the teachers' beliefs about the use of classroom assessment and the classroom assessment methods. In addition, this study showed that the teachers' assessment practices were shifted from using various assessment methods to limited assessment methods due to the O-NET tutoring policy. Incongruence between the teachers' beliefs and practices could be influenced by the contextual factors such as educational policy, time constraints, excessive workload, and teacher's lack of assessment knowledge. The implications of the study were also provided.