In a line of research employing a survey instrument, the "Critical Thinking Belief Appraisal", teachers supported critical-thinking (CT) activities more for high- than low-advantage learners, likely exacerbating a "rigor gap" implicated in persistent achievement gaps. Such beliefs were less likely to be espoused by expert teachers than randomly selected ones, and teacher-education programs mitigated these beliefs but did not expunge them, suggesting a need for interventions that foster belief change. Six issues were found to be associated with support for low-CT activities with low-advantage populations--learners' prior knowledge, time constraints, influence of parents, influence of colleagues, learners' level of motivation, and learners' level of ability. The rigor gap may be ameliorated through teacher-education practices that encourage teachers to (a) reflect on their existing beliefs, their experiences as students, their field experiences, classroom scenarios, and models of best practice, and (b) create instructional plans featuring high-CT activities for low-advantage learners.