Analysis for a Cluster RCT

#1
I am conducting an analysis for a cluster RCT, where the clusters are schools. When I compare the intervention to the control group overall without assessing the impact of the intervention on specific clusters, there is no statistically significant difference in the continuous outcome variable between the two groups. How do I ensure that I also assess the impact of the intervention on specific clusters. The students in schools are being measured at 2 time points.