As explicit administrative expectations to use meaningful inquiry-based instructional activities and formative assessment tasks might influence teachers' classroom practices, this study assessed science teachers' use of contemporary educational activities and assessment tasks above and beyond their conceptions of traditional teaching and learning and their attitudes toward using final tests. Data were gathered from 127 primary school science teachers from 60 Israeli public schools. The results showed that although used less frequently than final tests, formative assessment tasks were used to some extent by the participants during learning processes. Partial least squares structural equation modeling results pointed to the mediating role of teachers' positive attitudes toward tests in linking their conceptions of traditional teaching to increased use of summative assessment tasks (final tests). Moreover, teachers who reported using constructivist educational activities, more specifically collaborative practices, also reported using formative assessment tasks. Contrary to expectations, this study's model did not point to a significant negative connection between teachers' traditional conceptions of teaching and learning and their tendency to use constructivist activities in their classes. It is inferred that in practice teachers need to respond to explicit administrative expectations to use meaningful inquiry-based instructional activities and formative assessment and therefore might use those activities in spite of their traditional conceptions of teaching and learning.