Many students at the Valley View Primary School (pseudonym) in the Caribbean are not performing according to numeracy and literacy standards on national tests. Administration and teachers wanted to know why changes to formative assessment practices are not increasing students' achievement levels. The purpose of this qualitative exploratory case study was to examine teachers' perspectives regarding the importance of formative assessments relating to their instructional practices and knowledge of formative assessments in this primary school. The study was guided by Xu and Brown's teacher assessment literacy in practice (TALiP). Nine participants were purposefully sampled. Research questions helped guide exploration regarding teachers' perspectives of formative assessment practices to support students' academic achievement in literacy and numeracy classes. Data were collected through semistructured interviews and document reviews regarding teachers' planning and assessment of instruction. Data were coded and analyzed using an inductive approach involving a priori, open, and pattern coding methods based on three constructs of TALiP, teachers' knowledge and conception of formative assessment, and teachers' assessment literacy in practice. Results indicated a gap in teachers' knowledge and application of formative assessments in classrooms. These findings led to an action plan to support teachers' formative assessment practices. This action plan can lead to effective social change in terms of increased self-efficacy and autonomy among teachers, higher student achievement, and school leaders who support teachers' professional growth and development. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]