This chapter outlines the steps necessary for balancing innovation with maintaining reliable and valid trend measures in international large-scale assessments (ILSAs), using PISA 2015 as an example. New scaling methods are introduced that involve concurrent calibration, accounting for item-by-country, item-by-language, and item-by-cycle interactions, and more general IRT models. The goal is to establish approaches that allow for more comprehensive measurement invariance testing, the exploration of the impact of different assessment modes when moving from a paper-based to a computer-based administration, and to provide a better model-data fit and more robust item parameter estimates while maintaining trend measure integrity. The presented methods can be adapted for other large-scale assessments and can also be used for further research on measurement invariance.