In our immersion programme we don’t use Dutch as an intermediate language. Any new word is directly connected to the object or concept it stands for, or it is explained in English. This practice is corroborated by recent research. Jeanet van Hell investigates learning and teaching English at Dutch primary schools.
A remarkable finding: a second language can be mastered at any age. However, the pronunciation will be perfect only when learnt at early childhood from a native speaker.
Read about Van Hell’s research at http://www.ru.nl/wetenschapsagenda/@774053/laat-native-speaker/