Biologists, lay adults, and children alike value understandings of how biological entities work, prioritizing these mechanistic explanations in learning choices from at least five years of age and onwards. Despite this, formal education of young children has historically lacked mechanistic content, reserving these types of causal explanations for older students. We explored strategies by which mechanistic explanations may be emphasized to learners, identifying asymmetries between teacher intuitions and the influence of a mechanistic focus on young children’s science learning. In Study 1, we contrasted K-12 teacher intuitions about two types of learning goals—mechanistic or labels—in elementary school biology lessons, assessing general preferences and beliefs about which goal would maximize learning. Teachers preferred labels-focused learning goals when considering first and second grade lessons, but increasingly shifted to mechanistic learning goals for third through fifth grade lessons. In Study 2, children ages 6 to 11 were given either a mechanistic or a labels-focused learning goal prior to watching a video lesson about the heart. In Study 3, children ages 6 to 9 heard either a mechanism-focused or labels-focused description of the small intestine prior to viewing the target heart lesson. For both learning studies, children of all sampled age groups guided to focus on mechanism performed better on a learning assessment than those guided to focus on labels. While teachers believe that younger students benefit more from superficial goals such as labels, we find that mechanistic goals enhance learning even among the youngest children. We discuss implications of initial emphasis of mechanistic science content in early elementary school to boost subsequent learning outcomes and science interest.