To understand how different instructional practices and instructional regimes support students learning is central to quality in schools. A child's potential outcome under a given instructional regime / and or method depends on peers and teachers, and oth er supporting resources. Exploring how different instructional regimes work to improve student achievement requires the need for multilevel methods that would validate causal inferences on a complex data set. Therefore we need models and studies that are able to bridge different levels of the system and data sources (e.g. schools, teachers, students) of relevance for understanding intended, experienced, and performed instructional regimes. There exists however no straightforward way and/ or methodology to handle this challenge today. There is an obvious request for analytical models, research designs and required data sets able to link differences between intended instructional regimes and the regime actually enacted. Studies that measure classroom instru ction are accordingly central to this research agenda. The aim of this pre-project is therefore to identify and evaluate models that enable us to bridge possible relation between process data and achievement data, when it comes to (optimize) students' lea rning.