The aim of this study was to examine how fifth grade students' critical thinking and problem-solving skills can be developed using practices based on Newman and Weglage's (1993. Five standarts for authentic instruction. "Educational Leadership," 50(7), 8-12) authentic learning standards ("high-order thinking," "depth of knowledge," "relation with the world beyond the classroom," "constant conversion" and "social support for student achievement"). The main aim of the study was to offer different perspectives on mathematics education by focusing on development of critical thinking skills needed to understand mathematics. The study was carried out in six cycles via an action research model. The data consisted of unconstructed observations (camera recordings), students' scores on CTR (Critical Thinking Rubric), and their journals and written documents. The research results showed that practices based on authentic learning standards improved such critical thinking skills as comprehending, comparing, proving, suggesting new solutions, and reflecting on problem solving processes of the students who were included in the target study group.