This study examines how classroom activities, student gender and student personal interest in science studies and careers predict situational interest in physics learning. Teaching modules were designed based on the secondary physics curricula in Finland (Helsinki) and Chile (Santiago and Viña del Mar) emphasising students engagement in scientific practices. The study was implemented in four classrooms in both countries. Data on situational interest and ongoing classroom activities were obtained using the experience sampling method, with measurements taken three times during a lesson. The process yielded a total of 1717 measurements in the Finnish schools and 1767 in the Chilean schools. Multilevel regression analyses with mixed effects and random intercept were conducted. Results showed a positive effect of scientific practices that required asking questions, designing scientific inquiry and interpreting data on situational interest. Student collaborative situations were more interesting for Chilean students than for Finnish ones. In terms of gender differences, on average, Finnish male and female students experienced the same level of situational interest, while the situational interest of Chilean female students was higher than the average of male students. Personal interest in science studies and careers was the best predictor of situational interest in both countries.