The study aims to characterize contextual learning during class visits to science and natural history museums. Based on previous studies, we assumed that "outdoor" learning is different from classroom-based learning, and free choice learning in the museums enhances the expression of learning in personal context. We studied about 750 students participating in class visits at four museums, focusing on the levels of choice provided through the activity. The museums were of different sizes, locations, visitor number, and foci. A descriptive-interpretative approach was adopted, with data sources comprising observations, semistructured interviews with students, and museum worksheets. Analysis of the museum activities has yielded four levels of choice that affect learning from no choice to free choice activities. The effectiveness of learning was examined as well by looking at task behavior, linkage to the students' prior knowledge and their school's science curriculum, and linkage to the students' life and experience. Our findings indicate that activities of limited choice offered scaffolding, allowed the students to control their learning, and enhanced deeper engagement in the learning process. Within all the choice opportunities, the students connected the visit to their own life experiences and to their prior knowledge, even when the guided activity scarcely addressed it. Critical responses were obtained mainly when the museum environment allows a variety of learning opportunities without directing the students.