There is growing evidence of the efficacy of evidence-based interventions in improving the academic and social outcomes of children who exhibit challenging behaviors during program implementation periods. However, less is known about the extent to which practices learned as part of these interventions are sustained after these projects end, when funding is paused temporarily, and in less-than-ideal conditions. This study used qualitative methods to investigate whether teachers previously trained in the BEST in CLASS-Elementary intervention continued to use the program's evidence-based practices with students 1-2 years after completing the program and in the context of the COVID-19 pandemic. It also examined teachers' perceptions of the impact of practice use on students' academic and social outcomes. Thirteen BEST in CLASS-Elementary teachers from elementary schools in two southeastern states in the USA where the program was implemented completed semi-structured interviews on the topic. Data were coded thematically, and the results indicated that over 50% of teachers reported using "rules," "supportive relationships," and "praise" frequently with their students. However, "precorrection" and "opportunities to respond" were reportedly used less often. Teachers also perceived that their use of these evidence-based practices was linked to increases in their students' academic engagement and academic performance and knowledge, improvements in students' behaviors, their relationships with teachers, and general comfort and self-confidence. The discussion highlights modality-specific patterns noted in the results that might influence sustainment and the implication of these findings for interventions and programs aimed at promoting positive behavioral outcomes for early elementary school students.