In today's world of information explosion, independent lifelong self-regulated learning (SRL) is becoming a necessity. However, opportunities in schools to experience such learning modes are relatively rare. This long-term explorative field study examined students' SRL of science. Changes in students' self-reported and enacted SRL in two ninth-grade science classrooms were measured over the course of a full academic year. The self-regulating (SR) class (n = 25) studied genetics while self-regulating their learning. The teacher-controlled (TC) class (n = 27) studied the same content in a teacher-regulated mode. Data were collected at several time points along the year by SRL questionnaires (Learning and Study Strategies Inventory, LASSI), science knowledge tests, and (in the SR group only) protocols for measuring enacted SRL. Findings showed that enacted SRL correlated with self-reported SRL, validating measurements. The SR students outperformed their TC peers in science learning. Significant changes over time in both self-reported and enacted SRL emerged only for the SR students, suggesting that long-term SRL practices may promote awareness of learning processes and ability to apply SRL. Implications for school learning are discussed.