Teacher education can be regarded as a lifelong-process. Its outcomes have an effect on the quality of instruction and consequently on students’ learning results. In general, teachers have formal or informal opportunities for professional development. Research in this area supports the assumption that the willingness to attend, for example, in-service-trainings depends on formal qualification, work experience but may also be affected by their current situation. The focus of this paper is to further understand the use of in-service training of teachers in German primary schools. This is of interest because in Germany teachers are required to participate regularly in training and development, but they are rather free in choosing from a wide range of offerings. It also can be found that about 40 percent of all Grade 4 learners are taught by not fully qualified teachers. Research supports two different hypothesis how this might affect the use of in-service training. On the one hand it can be assumed that out-of-field-teachers may feel the need to attend trainings as they provide structured learning opportunities in order to obtain necessary subject knowledge (“deficit hypothesis”). On the other hand research suggests that teachers rather tend to choose trainings in a subject that corresponds to their major (“interest hypothesis”) to expand their professional competencies in that field. In this paper we analyze to what extent primary school math teachers at different stages of their career and with different qualifications differ in their use of in-service training. The analysis is based on information given by German math teachers teaching 4th-grade students surveyed in in TIMSS 2015. To understand differences in participation in trainings for professional development regression models were calculated using the IEA IDB Analyzer. Missing data was imputed using FIML. Apart from the (formal) qualification, gender and years of teaching were considered as teacher variables (N = 224). Preliminary analysis show support for both the interest hypothesis as well as the deficit hypothesis: There is no significant difference in the frequency of participation in professional development programs between teachers who studied mathematics as a major and those that did not study mathematics. However, teachers who studied mathematics as a minor show a significant lower participation rate. Teachers with a major in mathematics tend to participate more often in in-service training focusing on mathematics content or curricula, whereas teachers that did not study mathematics tend to participate more often in training focusing on instruction/mathematics pedagogy.

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