It is important to address social and emotional concerns early on, as they can adversely affect learning at all levels. The classroom is an ideal context for fostering healthy social and emotional development. For example, emotion regulation can be reinforced through simple daily practices within schools. The current applied research project was in collaboration with multiple community partners and assessed the effectiveness of a classroom-based HeartMath practice (Heart Lock-In) on resting heart rate variability (HRV) and self-reported emotional benefits in elementary students. This repeated-measures study was conducted in central Alberta, Canada, in 2020 and involved obtaining pre-post HRV measurements from N = 24 grade five students who participated in a teacher-led 5-min Heart Lock-In (like loving-kindness--radiating love to oneself and others) daily for 4 weeks. We hypothesized that the practice would increase resting HRV compared to a 4-week relaxation control. Qualitative questions were included to capture perceptions of the utility and impact of the practice. Univariate analysis of variance revealed that the HeartMath intervention significantly increased HRV compared to the relaxation control. Students reported enhanced emotional stability, feeling more positive about themselves, and improved interpersonal relationships. They expressed that the practice gives them better focus, which helps us to improve their performance (e.g., in academics and athletics). These findings provide evidence that a simple and short HeartMath ER practice can be practical for school educators, administrators, and counselors to implement in the classroom.