436 students of grade 8-10 worked with a computer-based experimental environment representing a domain of physics. We examined the impact of strategic experimenting on learning out-come considering prior knowledge as a potential moderating variable and intelligence, motivation, and strategy knowledge as control variables. We focus on a strategy called Isolating Variables (IV; cf. CVS: Control of Variables Strategy) that has not consistently been conceptualized in the literature so far. For a clear terminology we distinguish two types of the IV strategy (IV-between and IV-with-in), and we investigated the IV-between type empirically. We found the use of the IV-between strategy as a substantial predictor for learning outcome, independent from which of the three control variables is included in the prediction model. However, the predictions are moderated by prior knowledge. The results are discussed concerning the usefulness of the proposed distinction between the two types of the IV strategy and concerning theoretical as well as practical implications.