Science education reform documents call for students to learn science by engaging in inquiry and using science practices. One such science practice is constructing evidence-based explanations. Few students enter community college science classrooms having experience with, or being proficient in, using evidence to explain scientific phenomena. Therefore, we used a claim-evidence-reasoning framework to scaffold students as they learned to construct evidence-based explanations in an introductory environmental science course at a regional community college. We gathered pre/post and unit tests as well as lab reports to examine students' explanations throughout the course and found strong growth in students' tests scores but very little growth on the lab scores. In addition, we found that students struggled most with the scientific reasoning component of explanations. We discuss the interconnectivity of science practices when engaging in authentic labs. Without knowledge and skill in other science practices, such as finding patterns in data and using mathematics and computational thinking, students will likely struggle with constructing evidence-based explanations. We provide two main recommendations for engaging students in authentic science in the laboratory component of a class.