In contrast with other early-tracking education systems, schools in the Dutch system can provide several combinations of school tracks during the first years of secondary school. We study how the attended type of track(s) affects students' chances of obtaining a pre-academic school certificate. Our target group is students just below the margin of entering the pre-academic track. We differentiate between strict tracking and two forms of mixed tracking, including either one pre-academic track (partly mixed) or both pre-academic tracks (broadly mixed). We examine whether our target group obtains a pre-academic degree directly or indirectly via stacking certificates. We use an instrumental variable (IV) approach to estimate causal effects. Our results show that students' are more likely to obtain a pre-academic certificate when they attend mixed tracks that allow for upward mobility, i.e., comprise a pre-academic track. High-SES students are more likely to attain a pre-academic certificate indirectly via stacking certificates. We conclude that our nuanced analysis contributes towards a better understanding of the causal effects of tracking on individual student outcomes. The downward trend in mixed tracks in the Netherlands should, from an attainment perspective, be encouraged to be reversed.