In the last decade, several efforts have been made to foster language acquisition and development of young children in preschools before school entry in Germany. In particular, pull-out interventions in small group settings and/or integrated approaches with embedded learning activities and language modeling were applied in early education settings. However, not all of the applied language promotion approaches in early education are empirically evaluated. This systematic review aims at the identification of evidence-based language promotion approaches in the early years and discusses the quality of evaluation studies and the validity of results. The review consists of intervention studies measuring the impact of language interventions for children from 1 to 6 years of age in center-based care in Germany. Only (quasi-) experimental studies with at least 10 participants per condition were included. The intervention studies were published or results were presented at conferences from 2000 to 2013. Selection criteria, content, and study quality were reviewed by two independent coders. A multiple-step coding procedure was performed with (a) title and abstract screening; (b) screening of selection criteria, study design, and bias index; and (c) coding of intervention design. The whole literature was double-coded and disagreements were solved through repeated reading. The electronic and hand search yielded 3,897 potential literature hits. After screening, 23 (quasi-) experimental studies were identified. The validity of the results of these studies was rated through a bias index. Only eight studies met basic standards for effectiveness research. In the review, study outcomes were distinguished between language approaches administered in infant-toddler classrooms (under the age of 3 years) and interventions in preschool/kindergarten settings (3 years and older). The results based on two studies showed positive effects of integrated approaches in center-based care to foster language development of children under the age of 3 years. The impact of language interventions for children aged 3-6 years was inconsistent. An equal number of studies demonstrated the positive effects as well as no effects of additive pull-out programs or integrated approaches on the language development of children 3 years and older. Overall, the findings suggest great variability in the implementation of single language promotion interventions. More research is needed to investigate whether there are inconsistent results because of limited study quality or the inadequate reliability or sensitivity of language assessments, or whether they appear because the interventions are ineffective in fitting the developmental needs. Further, it is still unknown whether there is a feasibility problem in general or whether there is not enough support for early education teachers to implement language promotion programs with high fidelity.
