Vocabulary development in the early school years. Association with demographic factors, formal schooling and summer vacation, and the effects of a teacher Continuing Professional Development program.

Background: Well-developed vocabulary skills are crucial for academic success. Students having the language of instruction as a second language and students from lower socioeconomic backgrounds often have lower performance on vocabulary assessments. Teachers play an important role in supporting the vocabulary development of all students, regardless of background and educational needs.
Aims: To investigate how summer vacation and formal schooling, as well as demographic factors such as level of parental education and bilingualism, are associated with vocabulary development in the early school years, and to
evaluate the effects of a language and communication focused teacher Continuing Professional Development (CPD) program on both the participating teachers and on the vocabulary development of their students.
Methods: The CPD program was delivered to teachers (n = 25) serving children in grade one and two (n = 209; age 6 – 9 years) and consisted of 11 weekly 90-min sessions introducing hands-on strategies to enhance language learning opportunities and interactions in the classroom. Both teachers and their students were assessed pre, post and at three months follow up after the CPD. Teachers were assessed with self-reports on activities and interactions in the classroom, and their self-efficacy of classroom management, as well as with qualitative analyses of statements made by the teachers in structured conversations. Students were assessed with a test battery targeting a broad range of language skills (including a Semantic Verbal Fluency/SVF task, and a Word Definition/WD task), as well as a non-verbal cognitive test. Background information was collected through parental questionnaires.
Results: Paper I: SVF performance was negatively affected by summer vacation and positively affected by formal schooling. Variance in development could not be predicted by bilingualism, level of parental education, general
language ability, or non-verbal ability. Paper II: Monolingual students outperformed bilingual peers on the WD task. However, bilingualism alone could not explain the variance in performance. Paper III: The CPD was well-received and appreciated by the teachers and qualitative analyses indicated signs of increased knowledge. However, no statistically significant effect was seen in self-reports on activities and interactions in the classroom, or self-efficacy of classroom management. Paper IV: The CPD might have a positive impact on the students’ WD performance, but not on the SVF performance.
Conclusions: There is an interaction between several factors associated with students’ vocabulary development, and no factor in isolation can explain the variance in performance. A CPD program of this sort may result in some signs of change in teachers’ knowledge and their students’ WD development, but there is no guarantee that taking part in a teacher CPD results in clearly improved teacher or student outcomes.