Recent European reports have placed teachers at the center of education improvement efforts (Bokdam et al., 2014; Osborne & Dillon, 2008). To help students learn what they need to learn, teachers must understand the topics they are required to teach (van Driel et al., 2014). Scholars have studied this component of teacher knowledge, known as subject matter knowledge (SMK), for years and found that SMK influences teachers’ instructional practice (e.g., Sanders et al., 1993), interactions with students (e.g., Goodhew & Robertson, 2017), confidence (e.g., Appleton, 2006), as well as the learning of their students (e.g., Sadler et al., 2013). Despite its importance, studies have repeatedly found that many teachers do not have adequate SMK (van Driel et al., 2014), often holding the same misconceptions as their students.

In order to support the development of teachers’ SMK, teacher educators have designed formal professional development (PD) programs which engage teachers in learning activities designed to support their SMK. While these programs have important impacts, the availability of resources limit the number of teachers that such programs can reach (Bokdam et al., 2014). Because of these limitations, other modes of supporting teacher learning of SMK must be explored and pursued.

One of these alternative modes of supporting teacher learning is learning through teaching experience, which has been called informal learning (Grosemans et al., 2015) or everyday learning (Kyndt et al., 2016; Louws et al., 2017). This refers to learning that occurs as teachers engage in the normal activities of their work that are not designed or moderated by external actors (see Kyndt et al., 2016). Existing research into this mode of learning has explored the different activities teachers engage in to learn. A major review of this literature classified these activities into seven major categories: 1) interacting and discussing with others, 2) practicing and testing, 3) learning from others with no interaction (as when observing another teacher), 4) consulting information sources, 5) reflecting on/in action, 6) engaging in extracurricular activities (outside of their work), and 7) encountering difficulties (Kyndt et al., 2016).

Prior research in this area has only infrequently explored teachers’ learning of subject matter (Kyndt et al., 2016). Instead, studies typically explore learning how to teach, whether focusing on teachers’ pedagogical content knowledge (Chan & Yung, 2015) or socialization into a school (Kyndt et al., 2016). Few studies have considered teachers’ learning of SMK through everyday teaching experiences (Bokdam et al., 2014; Kyndt et al., 2016).

Several scholars have proposed multiple models for how learning through experience proceeds (Dewey, 1933; Eraut, 1994; Schön, 1983). These models agree that learning must begin with a “shock” (Dewey, 1933, p. 12), something that “arrests direct activity temporarily” (p. 107). The shock leads to the person reflecting on the experience, whether during the experience or shortly thereafter. This reflection has been characterized in multiple ways, but each characterization captures some form of sending some time to make sense of the experience.

Using this two-step model, we explored the process of primary teachers learning science SMK through everyday teaching experience. The research questions that guided this study are:

1. What prompts primary teachers to recognize what they do not know in their science SMK while planning or teaching?
2. What actions do primary teachers take during planning or teaching to improve their science SMK?
3. How do teachers with high SMK differ from teachers with low SMK with respect to learning science SMK through teaching experience?

Participants in this study were 27 primary teachers in grades 5 or 6 (children 9-11 years old). These teachers were responsible for instruction in all main school subjects: literacy, mathematics, social studies, and science. These teachers were purposefully selected from a sample of participants in a larger study involving 438 teachers (Author, 2019) to reflect different levels of science SMK. In the previous phase of the larger study, teachers completed a test of their science knowledge for topics they were responsible for teaching with items selected from the Misconceptions-Oriented Standards-Based Assessment Resources for Teachers (MOSART) test bank (Sadler et al., 2010). Half of the participants (14) had scored “high” (more than 13 of 16 items correct) on the test and the other half (13) had scored “low” (less than 12 items correct). Participants completed 30-60 minute semi-structured interviews in which they were asked to reflect on people, places, and events, both in and out of school, that influenced their science SMK. Analysis focused on their responses to the following questions: • Tell me about a time you were planning science instruction and you realized you didn’t know something. How did you know you didn’t know? What did you do? • Tell me about a time a student asked a science question and you didn’t know the answer. How did you know you didn’t know? What did you do? • In general, where do you go when you have questions about science? Who do you go to when you have questions? To avoid biasing the interviewer, researchers conducting the interviews were unaware of the group to which the teacher belonged. Interviews were recorded and transcribed verbatim. These data were analyzed interpretively by, first, having two researchers independently review a sample of six teachers’ interviews to formulate a list of emergent themes related to each research question. These researchers then met to compare, clarify, and revise the codes. Using these agreed upon codes, all remaining participant responses were coded by both researchers, who then met to finalize consensus on the codes. To ensure the rigor and validity of analysis, an active search for confirming and disconfirming evidence was made. During the previous steps of analysis, researchers were not informed of participants’ groups to avoid biasing the analysis. During the final step, participants were identified as high- or low-SMK and the codes between the groups was compared.

RQ1. Participants reported recognizing not knowing something when they were reflecting on their own SMK during planning. One participant, Herb Jacox, reported: “I knew about the equinox, but I didn’t understand what it meant and why they happen on the days that they happen.” Participants also recognized not knowing something when they considered student questions. Alisha, for example, described how her students’ questions helped her: “…usually, I find out that I don’t know something when the kids ask me about it.” RQ2. Following the recognition that they didn’t know something, participants asked others for help. For instance, Rhonda said: “If I didn’t know I would go to [another teacher] and say, ‘…Do you understand it?’” Participants also asked family members (e.g., their husband) for help. Teachers also read or watched content resources when they recognized not knowing something. Several talked about “Googling” something or turning to books. RQ3. One difference between high- and low-SMK teachers was identified. High-SMK teachers were more concerned with turning to expert sources than low-SMK teachers. For example, high-SMK teachers frequently spoke of asking those with demonstrated science expertise for help. Similarly, high-SMK teachers spoke of reading websites hosted by credible organizations. In contrast, few low-SMK teachers talked about the reliability and quality of the resources they referenced. This provides insights into informal continuous professional development called for by a European report (Bokdam et al., 2014) and adds to the literature on teachers’ learning through everyday teaching experiences (Kyndt et al., 2016) by exploring primary teachers’ learning of SMK. One implication is that teacher educators should help all primary teachers have access to experts. This could include cultivating relationships with experts, such as science faculty, who are willing to assist primary teachers. These findings also indicate the importance of helping teachers quickly identify reliable websites.

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