There has been an increased use of authentic practices in both science and environmental education in recent years. Such practices can utilize social constructivist frameworks to consider the learning that may be taking place as students become engaged in tool use. The current study focuses on a group of elementary school students studying the Everglades in the field and in a classroom setting during one academic year. In particular, we observed students' use of tools (identified as tool-conventions to include both artifacts and conventions) and compared their use in both settings. We found that in the field, students spent considerable amount of time engaged in data collection activity such as taking observations and measurements that resembled what scientists might be doing and included the invention of new tools to facilitate data gathering. In this context, students generally worked more independently from the teacher, collaborated in small work groups, and engaged in more self-directed inquiry. In the classroom, while some of the scientific field tools were practiced in anticipation of their use in the field, activity included more teacher direction, often resembling what might be found in other types of classroom work and the tools used there often supported this work. Models of tool use based on Yrjo Engestrom's activity approach were constructed for both settings. Implications of the results include the importance of viewing tool use in authentic learning with a sociocultural and activity perspective to reflect the socially constructed nature of such learning. (Contains 5 figures, 1 table, and 3 endnotes.)