This study is about five children with disabilities in a fully inclusive preschool and their involvement in learning throughout teacher-initiated instruction sessions. Involvement matters for the children and refers to attendance, concentration on tasks and the child’s interest in preschool activities. Its first aim is to investigate the children’s involvement in learning during group instruction sessions, such as circle times. Since their involvement is not observed to be high, the second aim of the study is to investigate and discuss (a) whether the children’s involvement in learning changes when instruction sessions are provided one-on-one and (b) if one-on-one instruction and full inclusion work together. One-on-one instruction refers to a teacher instructing a child and is often for children with difficulties in learning. The design used was a single case research study. The teachers also shared their views, and these were collected. The results show positive change across participants. For all children, the percentage of exceeding the median was 100%, which is indicative of very effective intervention. The intervention provided new insights relating to children’s knowledge and one-on-one instruction in a fully inclusive preschool. The study can form a basis for important preschool discussions.