Due to historical reasons, schools in Sri Lanka have a high level of segregation - by language, sex, ethnicity and religion. It will not be easy to desegregate the schools, but at least opportunities can be provided for students to collaborate with other schools (perhaps as Twin Schools).
This would be a few periods (maybe every 2 weeks) where a group of students from 2 (or more) schools meet. This could be for the Current Affairs / Critical Thinking idea, it could be an art project, it could even just be games (actually games are the best thing they could do in terms of developing empathy and the ability to communicate effectively in heterogeneous environments, both of which are crucial for life and work in the 21st century)
Like with our other proposals, this should be optional - students who don’t want to participate should not be forced to