This study aims to uncover some key elements of successful home-learning of mathematics, based on students' perceptions, during the COVID-19 pandemic and offer recommendations for mathematics learning beyond the crisis. Throughout our work, we aimed to examine students' reflections on mathematics learning and learning environments that assisted their ease of transition from in-school face-to-face learning to home-schooling during the COVID-19 isolation. In this paper, we will present how mathematics learning has changed for upper secondary school students in Austria and outline students' perspectives in relation to their new learning experiences during the period of school closures. Through the use of case study principles enhanced by some design-based research approaches, we were able to illustrate that (a) familiarity with the context, (b) problems or tasks as learning triggers, (c) mathematics learning as a social as well as individual process, and (d) perceived positive cost-benefit analysis of learning mathematics are key to students' learning success. Although these categories were key for the students when learning mathematics in home-schooling during the current crisis, these categories could be equally considered when education moves back to school or in mixed learning environments post COVID-19.