Contents: Maie Soll: Why this study? A view from the Estonian ministry of education and research - Krista Uibu/Kristiina Tropp: Bilingual and monolingual students' linguistic competences and their development at Estonian primary school - Eve Kikas: Cognitive abilities and math achievement of students from Estonian-, Estonian-Russian-, and Russian-speaking families in Estonian-language classrooms - Kristina Seepter: Longitudinal explorative study of mono- and bilingual pupils' differences in math achievement: the role of Estonian and Russian instructional environment - Anu Palu/Reelika Suviste/Eve Kikas: Errors in solving arithmetic word problems. Differences between students from Estonian- and Russian-language schools - Piret Soodla: Teachers' judgments of monolingual and bilingual students' reading skills: child-, class-, and teacher-related factors - Kristina Seepter: Relations between mono- and bilingual pupils' math achievement and teachers' knowledge of special education needs - Aivar Ots/Margit Tago: Bilingual student well-being in submersion education: changes in self-esteem and school satisfaction during the fourth grade - Grete Arro: Development of self-reflection ability and its relations to scientific concept thinking in mono- and bilingual children: are bilinguals doing better? - Hanna Reek: Ethnic stereotyped attitudes in relation to social relationships in fourth grade students - Aaro Toomela: Children studying in a wrong language: looking for ways to improve.