Classroom-based surveys are a proven method for studying adolescents since it is relatively easy and cost-effective to obtain a large number of participants from various backgrounds. They are also beneficial for research on youth radicalization and extremism. For example, they allow us to acquire information such as the percentage of students that hold extremist attitudes, factors that correlate positively or negatively with extremism, or how the process of radicalization develops over the course of adolescence. However, classroom-administered survey studies are not without challenges. In this paper, we describe various challenges we have encountered when using classroom-based surveys on extremism and radicalization in our research. We also present advice, including determining what sample design is appropriate, depending on the research question, when to employ a cross-sectional or a longitudinal design, how to measure general or ideology-specific youth extremism, how to achieve a sufficiently large sample size for quantitative analysis, and how to adapt the survey administration process when doing research on radicalization and extremism in a classroom environment.