In Estonia, as well as in other Baltic States, the society is multinational. The integration of its different ethnical communities is vital precondition of the state's stability and welfare. That is why from the year 1991 with the financial help of Canadian - Baltic program there were several projects realised, including the project "Immersion program of the second language acquisition". Its aim was to support Estonian as second language leaching to adults and pupils in the minority schools and preschool educational institutions, ensuring the succession of the Estonian language acquisition from the pre-school studies to the lifelong learning. The developed program now is successfuly realised in the schools. To ensure successful succession, now big attention is paid to the program's strong (the language knowledge, integration in the society) and weak (the parents' role in the study process, the quality of knowledge) points and factors that could influence the results of the project.