This study investigated the effect of various combinations of contextualization and teacher support on achievement and critical thinking. Two specially-designed sets of courseware were used to teach a unit on logic, one based on a single context and one based on multiple contexts. The participants were 151 9th graders in two vocational high schools. Each student was assigned to one of four groups: The first group used the multiple-context courseware with a teacher tutorial; the second group used the single-context courseware; the third group studied the single context courseware with a teacher tutorial; and the fourth group had a teacher tutorial only. Statistical analysis of two achievement tests on the unit and a critical thinking disposition inventory revealed that, regardless of whether the courseware employed single or multiple contexts, teacher support is beneficial. Findings are discussed in relation to comparable studies reported in the literature. Further research issues are raised in the last section.