The integration of scientific modeling into science teaching is key to the development of students’ understanding of complex scientific phenomena, such as genetics. With this in mind, we conducted an introductory hands-on module during an outreach gene technology laboratory on the structure of DNA. Our module examined the influence of two model evaluation variants on cognitive achievement: Evaluation 1, based on students’ hand-drawn sketches of DNA models and two open questions, and evaluation 2, based on students’ own evaluations of their models in comparison to a commercially available DNA model. We subsequently subdivided our sample (N = 296) into modellers-1 (n = 151) and modellers-2 (n = 145). Analyses of cognitive achievement revealed that modellers-2 achieved higher scores than modellers-1. In both cases, low achievers, in particular, benefitted from participation. Assessment of modellers-2 self-evaluation sheets revealed differences between self-evaluation and independent reassessment, as non-existent model features were tagged as correct whereas existent features were not identified. Correlation analyses between the models’ assessment scores and cognitive achievement revealed small-to-medium correlations. Consequently, our evaluation-2 phase impacted students’ performance in overall and model-related cognitive achievement, attesting to the value of our module as a means to integrate real scientific practices into science teaching. Although it may increase the workload for science teachers, we find that the potential scientific modeling holds as an inquiry-based learning strategy is worth the effort.