To understand the longitudinal effect of a technology-enhanced learning (TEL) environment with reflective guidance on sixth-grade students' learning in a photosynthesis unit in Shanghai, we designed a quasi-experimental longitudinal study with a pre-test and three post-tests, complemented by an examination of students' log data. Our findings show that TEL is useful in improving students' conceptual understanding and their retention of factual knowledge. Moreover, the regression analysis and the case study suggest that the time the students spent reflecting on ideas led to different levels of learning gains. In conclusion, these findings highlight the potential benefits of using TEL environments and illustrate the need to identify students who need extra guidance to engage in in-depth learning.