Time spent ‘learning foundational concepts in the sciences’ was the only activity associated with higher gains in both SMK and KOSM (i.e., an increase in exposure or time spent predicted larger gains). The difference between participants who reported “Always” spending time on learning these concepts and those who reported “Never” spending time was about two tenths of a standard deviation in their scores, equivalent to the average gains teachers would make in ten years of experience teaching.

Participants reporting that they attended the program because it ‘provided an opportunity to learn new or innovative methods of teaching science’ or ‘looked fun, challenging, or personally rewarding’ tended to have higher gains in both SMK and KOSM, between 7% and 12% of a standard deviation in scores, equivalent to between five and eight years of experience teaching.

Associated with decreased SMK gains, but not changes in KOSM gains:

• Time spent ‘designing student field trips,’
• Time spent ‘learning the newest scientific thinking on a topic,’
• Time spent ‘observing and critiquing classroom instruction’

Associated with decreased KOSM gains, but not changes in SMK gains:

• Time spent ‘designing assessment tools for the sciences’
• (Perceived) goal of the program was to increase knowledge of ‘something else’

Associated with decreases in both SMK and KOSM gains:

• Time spent ‘developing original curricula or activities’

Notably, and perhaps surprisingly, program duration showed no significant association with either SMK or KOSM gains. However, this may be due to the fact that all of the programs studied were summer PD programs of a relatively short duration.

Many program features were not found to be associated with statistically significant differences in gains. Program features showing no differences include:

• if program was conducted as an online, overnight or day program;
• whether research scientists, science educators, or other people were involved in presenting the program;
• whether the (perceived) goal of the program was to increase participants’ science content knowledge, pedagogical content knowledge, or curricula knowledge.

Most of the PD activities showed no significant association, including time spent:

• learning reformed pedagogies (e.g., Active Learning, Inquiry-Based Learning, or the Modeling Method of Instruction);
• learning strategies for incorporating science content, cross cutting concepts or science and engineering practices into the curriculum;
• participating in lectures or workshops led by research scientists or science educators;
• learning strategies for using simulations, collecting and/or analyzing data or collecting information from the internet in the classroom;
• conducting or assisting with scientific research;
• collaborating with colleagues in the same domain, grade or geographic area.

General experience: All else equal, experienced teachers tended to improve their science content knowledge more than inexperienced teachers.

Prior science experience: Teachers with experience in science (any kind of science) improved equally well, but teachers who had never taught science before tended to make fewer improvements to their science content knowledge.

Grade band experience: Finally, teachers who had only ever taught classes in a different grade band (and so were attending a PD for a grade band in which they had no prior experience) also showed less improvement in their science content knowledge than teachers who had previous experience teaching that grade band.