The aim of this dissertation was to provide a deeper understanding on how to support multilingual children’s mathematical skills in early childhood education and care (ECEC). Research has shown that multilingual children tend to have weaker mathematical skills than their monolingual peers as early as the first grade. However, the diverse multilingual settings in which mathematical teaching and learning occur today as well as the traditional monolingual perspective in pedagogical practices pose a challenge in terms of providing effective support. The purpose of this dissertation is to offer new perspectives on supporting mathematical skills in ECEC that would broaden the traditional practices to be equal to all learners including multilingual children.

The dissertation consists of three studies and a summary section. The aim of the first study was to investigate how the Count How Many -intervention (CHM) supports the early numeracy and oral language skills of multilingual children. The CHM intervention is intended to promote spontaneous focusing on numerosity (SFON) and to enhance skills related to counting and cardinality understanding. Although the intervention was not initially designed for multilingual children, its engaging, accessible, and hands-on early numeracy activities were expected to be effective also for multilingual children, as these activities allow participation even with a limited vocabulary. A prior study conducted with children whose first language is Finnish indicated that the intervention effectively supports early numeracy and oral language development (Hannula-Sormunen et al., 2020). In Study I, the effectiveness of the intervention was investigated for the first time with multilingual children.

A total of 48 children participated in the Study I, of whom 16 were multilingual. The multilingual children participated in the CHM intervention. Pairwise-matched monolingual children were selected for the two control groups. One of the control groups (n = 16) participated in the same intervention as the multilingual children, while the other control group (n = 16) underwent the early literacy intervention Let’s Read and Talk. Children's numeracy and oral language skills were measured at pretest before the intervention, at posttest after the six-week intensive phase, and at a delayed posttest after the five-month rehearsal phase. No statistically significant differences were found between the groups in the measurements. Thus, the results showed similar development of numeracy skills and oral language skills in the multilingual group in comparison to matched monolingual groups of children.

Even though the CHM intervention appeared to hold promise as being beneficial to multilingual children’s numeracy skills, Study I suggested that a deeper investigation into effective support strategies for multilingual children’s mathematical skills within ECEC would be valuable. Therefore, the following studies focused on identifying research-based recommendations to enhance early mathematical skills in multilingual children (Study II) and reviewing the former early mathematical interventions implemented with multilingual children (Study III).

In the Study II, research-based recommendations were compiled from previous literature following the principles of thematic synthesis. Articles presenting recommendations for supporting the early mathematical skills of multilingual children were searched from the international and national databases. Only articles that explicitly focused on recommendations for promoting early mathematical skills within ECEC context were included. Ultimately, five articles published between 2011 and 2020 were included in the synthesis. The articles were reviewed according to the three-phase protocol of thematic synthesis, first coding the articles, then forming descriptive themes based on the coding of the recommendations, and finally forming an analytical model based on the descriptive themes. According to the analytical model, ECEC professionals can support the early mathematical skills of multilingual children by (1) making mathematical activities culturally relevant, (2) becoming aware of their own preconceptions about learning mathematics and language, and shifting the perspective from weaknesses to strengths, and (3) enabling versatile ways to participate in math talk on a regular basis. Synthesizing the recommendations complements the limited research literature published in Finnish on supporting multilingual children's early mathematical skills. The recommendations were reflected to Finland’s national core curriculum for ECEC. Thus, the results of this study can be used also to support the pedagogical planning in ECEC.

The systematic review and meta-analysis conducted in the third study aimed to investigate the current state of early mathematical intervention research involving multilingual participants. The systematic review included 24 articles that explored early mathematical interventions with multilingual children aged 3 to 5 years. The results revealed that numeracy emerged as the predominant focus of these interventions, followed by geometric, measurement, and patterns. In examining specific instructional features related to multilingual participants, the most commonly employed approach was the use of mathematical language, while the use of children's home language(s) and culturally responsive instructional approach were less utilized.

Of the 24 studies included in the systematic review, 17 provided sufficient data to be included in the meta-analysis. The average weighted effect size (g = 0.46, 95% CI 0.32, 0.59) of the interventions involving multilingual participants was small according to Cohen's (1988) criteria. No significant differences were observed between interventions utilizing mathematical language, home language, or culturally responsive instructional approach and those interventions that did not employ these pedagogical practices. The average effect size of the interventions with multilingual participants was smaller compared to former meta-analyses where the participants were mainly monolingual children. The findings suggest that current early mathematical interventions may not adequately meet the needs of multilingual children and could benefit from further development.

Overall, the findings of the dissertation suggest that the recommendations developed to support multilingual children's early mathematical skills have not yet been used to their full potential. In the future, it would be important to explore the impact of the recommended practices in ECEC on the development of early mathematical skills in multilingual children. The findings of this dissertation provide a broad theoretical basis not only for the development of interventions for multilingual children, but also for ECEC professionals to guide the pedagogical planning aiming to support the development of mathematical skills in multilingual children. Furthermore, the findings can be utilized in professional development for ECEC professionals and in current pre-service education, when the goal is to provide research-based information on how to support the early mathematical skills of multilingual children