When putting learners into pairs or groups for an activity, don't just put them with the same partner they're always with. You can be more creative than that, I'm sure!
Try to find learners who have something visible (or otherwise known to the teacher) in common when creating pairs or groups. For example, 'the purple eyeshadow team', 'the white shirt team', 'the tied-back hair team', 'the grungy clothing team', 'the Japanese learners' team'.
It's something I've been doing for a few months now. Though (deceptively) simple, it provides an obvious starting point for conversation and mutual interest between the people you've grouped together. Try it yourselves.