NARST 2013 paper The effect of lesson duration (45 vs. 60 minutes) on quality of physics instruction by Rainer Wackermann & Julia Hater Department of Physics and Astronomy, Physics Education Group Ruhr-University Bochum, Germany wackermann@physik.rub.de This study concerns the optimal duration of physics/science lessons. It builds on the knowledge base of a previous study, where videotaping of 80 lessons of 18 physics teachers in Germany revealed that less than 1.6% of lesson time was spent on transfer or concept linkage. One hypothesis is that lesson duration (45 minutes) is too short to allow completion of learning processes. Making use of a current transforming situation where some schools have changed to 60 minute lessons, this study follows an experimental pre-post-design. Two teachers from one upper level secondary school were videotaped under both conditions (n=14 videos). Main instrument is a category-based, high-inferent video analysis accompanied by a student and a teacher questionnaire and an expert rating of quality of instruction. Main finding is that the extra time is used in a potentially beneficial way; however the cognitive activation of students remains unchanged. We therefore conclude that professional development might be necessary to make full use of the extra time. In view of the small sample size, however, generalization of findings is not possible. Subject/Problem The origin of lesson duration is widely based on tradition and pedagogical intuition rather than on learning theories or empirical investigations. In Germany, the lesson duration was changed from 60 down to 45 minutes in the nineteenth century because it allowed students to help in agriculture in the afternoons (Fölling-Albers, 2008). Although this justification is clearly outdated today, schools continue in this tradition. Other European countries like Switzerland or Finland have similar lesson durations, with physics and sciences in general often taught as “double-lessons” (2x45 minutes). Outside of Europe there are slightly longer lessons in the case of South Korea (50 minutes) and in Canada or the US lesson duration may vary from school to school, sometimes even exceeding double lessons. Although some work has been done on “learn time” in the broadest sense (see Carroll (1964), Walberg, (1986), Aufschnaiter (2003), Seidel & Shavelson (2007)), at present there is no theoretical or empirical work concerning the optimal duration of lessons. An interesting piece of information concerning lesson duration stems from our own research. Wackermann, Trendel & Fischer (2010) conducted a professional development program for physics teachers in 2005/06. The study involved videotaping and was carried out under the condition of traditional 45-minute lessons. The analysis of 80 videos of 18 different physics teachers showed that only 1.6 % of lesson time was spent on decontextualization, transfer or concept linkage, which are important final phases of a learning process. The finding is especially astounding, since teachers received coaching with respect to organization of learning processes.