In the first class of Slovenian primary schools, two educators teach as a team, either two primary education teachers (i.e., class teachers) or one primary education teachers and one preschool teacher. The two teachers plan, implement and evaluate their pedagogical work as a team. Many factors contribute to the effectiveness of their teamwork, such as team goals, team rules, team communication, team members’ roles and tasks and problem- and conflict solving in the team. The aim of the study was to investigate:
(1) how first grade teachers perceive the effectiveness of their own teamwork,
(2) how first grade primary school teachers and pre-school teachers differ in their perceptions of the effectiveness of their own teamwork and
(3) how do they differ in their perceptions of the teamwork’s effectiveness regarding their number of years of service.

The study also examined (4) the relationship between the frequency of team planning, team teaching and team evaluation and self-perceived team effectiveness. The sample included 111 first-grade primary school teachers from different regions in Slovenia. The average age of the participants was 47 years, ranging from 23 to 63 years. With an online questionnaire, we collected socio-demographic data of the participants and measured the frequency of their team planning, team teaching and team evaluation, and the self-perceived effectiveness of their own teamwork. Primary education teachers and preschool education teachers, both teaching in the first grade of primary school, differed significantly in their teamwork effectiveness only in one item: “By solving problems as a team, we develop as a team”. Preschool teachers agreed more with this statement than primary education teachers did. We also found some statistically significant differences in self-perceived team effectiveness regarding the number of years of service, where more experienced teachers rated the agreement regarding common rules in team as more important in comparison to less experienced teachers. We found positive and statistically significant correlations between the frequency of team planning and the following aspects of teamwork self-effectiveness: team rules, team goals and team members’ roles and tasks. There was no significant correlation between team teaching and any of the aspects of self-perceived team effectiveness. The frequency of team evaluation showed the highest correlations with the studied aspects of the team self-effectiveness: with team members’ roles and tasks, team communication, team rules, problem- and conflict solving within the team. The results highlight the importance of team evaluation for overall team effectiveness. Team evaluation should be systematically planned and conducted regularly after each instance of teamwork, as it significantly contributes to various aspects of team effectiveness.

Keywords: First grade teacher, teamwork, team planning, team teaching, team evaluation, teamwork effectiveness.