The Communication Supporting Classroom Observation Tool (CSCOT) is used in the UK to identify how teachers support children's communication development. This study evaluates the feasibility and impact of collaborative training for teachers using the CSCOT, delivered by specialist teachers and a speech and language therapist. Classroom practice was observed twice using the CSCOT before the collaborative training (repeated baseline). Five teachers then received the collaborative training, informed by their baseline CSCOT results. The training consisted of detailed feedback, target setting and support from the school Special Educational Needs Assistant (SENA) over a period of 20 weeks. Five further teachers did not participate in this training but acted as a control group. The CSCOT observations were then repeated for all 10 classroom teachers. The total score of the CSCOT significantly increased for the five teachers who received training only. There was no increase during the repeated baseline phase, suggesting that the increase was due to the training. All five teachers who participated in training increased their use of their targeted communication-supporting strategies. The CSCOT can be used as part of collaborative training to increase teachers' use of communication-supporting strategies in primary schools in Brunei.