Martine van der Pluijm

55 Activities and strategies – a review of empirical interventions to transfer knowledge to parents, for instance, by reflection activities during coaching sessions. Therefore, based on our findings it is not possible to draw conclusions about the effectiveness of workshops. Finally, both a center-based and a home-based delivery of the intervention for lower-educated parents can be effective. Most studies directed at lower-educated parents that report positive results on oral language development train parents at home (4, 9, 10, 12, 14, 17, 26). However, four studies report positive results while using a center-based delivery (5, 11) or a combination of center- and home-based delivery (19, 22). This might indicate that the location is not decisive for the effectiveness of the intervention. However, there are good reasons to consider a combination of a center- and home-based delivery. Most interventions are implemented by researchers for a limited period, while it may be important to involve teachers to increase their commitment to the intervention principles. The relationships between teachers and parents at school may be a starting point for a sustainable collaboration to strengthen oral language development at home and at school (Wasik & Sparling, 2012). Implications for future research A limitation of this review is the small number of studies specifically directed at lower-educated parents. Despite our efforts, we were not able to find more studies that targeted only lower- educated parents or studies that reported results differentially for high and low educational levels of parents. This study is the first systematic review comparing the effects of interventions on children’s oral language development directed at lower-educated parents with interventions targeting more heterogeneous populations. Our review has several implications for future research. First of all, we recommendmore research specifically directed at the target group of lower-educated parents. In addition, studies should pay more attention to defining the target group. Many studies that we encountered lacked information about parental education levels. Researchers could distinguish at least three levels of education: the level of attainment of high school, below and above high school. However, it would be desirable to distinguish parental education levels more precisely. In particular, the group of lower-educated parents is much more heterogeneous than the often used criterion of ‘high school as the highest attained level of education’ would suggest. This group can vary in country of origin and mother tongue, culture, level of education, biography, life conditions, job or expectations, and type of immigration (Wasik & Van Horn, 2012). In addition, there are many parents with little or no schooling and minimal literacy skills in their first or second language, who are also struggling with their oral skills in the second language and with the notion that print carries meaning (Allemano, 2013; Beacco et al., 2014; Scheele, 2010). Many of these low- literate, lower-educated migrant parents differ from mainstream parents in their home literacy experiences, home literacy activities, their beliefs about what counts in educating children, and