After you learned to speak you learned to read, right?
So after the children have mastered the instrument note reading is introduced- and after 2 weeks they read. All new pieces are from then on read from a large paper and memorised the next lesson. That is why all performances are “by heart” – I love the English expression over the Dutch: ” uit het hoofd”
Each note is given a special character, so the children know where to find it once they read.