There are more and more Facebook groups born everyday – the social media dramatically changed our (professional) communication. Facebook as a communication platform became popular among teachers as well as students. These facts are emphasize of importance of network research in educational setting (Sumuer and Soner, 2014; Fehér, 2017). Our paper presents a mixed-methods study, in which we analyze the informal online learning communities (i.e. Facebook groups) on Facebook as a source of teacher professional development, based empirical results on social network research methods. Empirical background and aims of research. Facebook as a social network platform offer teachers a new and and easy-to-use way for professional communication, professional development and exchange of ideas and personal experiences (Trust, 2012; Macià & Garcia, 2016; Trust, Krutka and Carpenter, 2016). Coutinho and Lisbôa (2013) analysed of professional growth in informal settings, based on Interconnected model of teacher professional growth (Clarke and Hollingsworth, 2002), community of inquiry model (Garrison et al., 2001) and collaboration model (Murphy, 2004). We have also tried to implement a recently emerged social network analysis theories to reveal a hidden background structures of larger networks (Barabási and Albert, 1999), and to examine the role of weak connections (Granovetter, 1983). The aims of our research was: to investigate the effectiveness of social network analysis in educational research; to investigate the usefulness of teachers’ Facebook groups emphasizing professional development of participants. The main research questions of this study were the following:

1. How is knowledge sharing and/or knowledge building cultivated Facebook groups for K-12 educators?

2. How actively K-12 educators participate this groups?

3. Are the Facebook facilities support this activity?

4. What are the main obstacles of collaboration and knowledge-building?

At the first stage of the research we have studied the most popular Hungarian-speaking teacher communities on Facebook. After review of communities we have chosen 5 groups of them, with population of 15, 17, 567, 686 and 4770. We have collected anonymous data with Facebook application (Netvizz 1.3) from public groups. After that we have used Excel, Minitab and R for data analysis, and Gephi for visualization of data. At the second stage we have created an online survey for members of the choosen groups with Google Forms. During two weeks period 313 teachers completed the anonymous online questionnaire. Our survey consisted 14 questions regarding motivations, attitudes and opinions of participants activities on Facebook teachers groups. After the online data collection we conducted interviews with 10 teachers by Skype, each one was about 30 minutes long. The semi-structured interviews was recorded by mobile and analyzed by authors thoroughly.

According to main findings of research, we can conclude the following: 1. The teachers activity in the groups we have examined exhibited a power-law degree distribution. It means, that a very low percent of teachers (5-20%) are really engaged and collaborate (write post, comments) in this groups, however number of teachers participating groups growing rapidly. (In our presentation we will provide a detailed analysis of results with quantitave data and social network diagrams as well as). Most of them are only silent members (sometimes called lurkers), so it seems hard to evaluate of the usefulness of their participation. Very important question of further research is how can foster activity of lurkers and how to evaluate their self-improvement. 2. The most active participators (teachers) are about 40 years old, younger actors are rarely play leading roles in Facebook activities. We have not succeded to reveal the reasons of this fact, it requires further examinations. 3. Despite of popularity of Facebook, it is not supported adequately the effective collaboration. Other PLN (Professional Learning Network) solutions provide more sophisticated facilities (file sharing and management, shared editing, archive documents etc.) for teacher collaboration and development (Trust, 2012). 4. Based on qualitative interviews two major themes emerged: the most active teachers found Facebook-groups very useful and inspiring forums, they collaborated many colleagues and they are able to build new knowledge through group-activity. The second theme is about obstacles of usage: the continuous presence in the groups requires too much time; some abusive or offensive communication by other members of the group. We are planning to investigate the possibilities of fostering and supporting teachers activities in Facebook groups.

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