Science lessons in nature are appealing and potentially supportive of children's learning, but little is known about how and for whom they are effective. A within-subjects, experimental, mixed methods design was employed with 92 4th-graders to determine if, why and for whom science learning is better through outdoor, nature-based instruction (NBI) compared to indoor, classroom-based instruction (CBI). Moderating variables, including student socioeconomic status, gender, English Learner status and connectedness to nature and mechanistic variables of perceived stress, engagement in learning, attention, and impulsivity were evaluated. Though the physical conditions for NBI were less optimal, NBI supported science learning as well as CBI, and for a broader range of students. With CBI, child demographics had a significant impact on science scores. In contrast, with NBI, all students performed similarly, suggesting NBI is a supportive strategy for a broad range of students.