Halliday & Matthiessen (1999: 195):
Small human collectives: family, household, class (at school)General category: between 'conscious' and 'institution'.Particular features: common number (as institution: the class is ~ are writing a report)-, can be Senser (the family seemed to think that... ); pronominalised as it - they, not he/she, but self-referenced as we and addressed either as you or in third person (Do you eat together?/Does ~ do the household eat together?).