The Sustainability Advent Calendar - this advent calendar from 2018 is still relevant and although some of the ideas may be aimed more at grownups, this advent calendar suggests themes to think about during advent.
Tis the Sustainable Season - this advent calendar lists things you could do each day in December to reduce, reuse and recycle.
Christmas Around the World - not really an advent calendar but Country Living magazine provides 20 inspiring talking points and traditions from around the world to discuss and develop into your own class activities.
Kindness Advent Calendar - created by a Highland teacher, this kindness advent calendar uses small acts of kindness to make our community a better place this Christmas. Suitable for at school or at home.
Unicef and Paddington - priced at £25, Unicef have produced these advent calendars that provide vital resources and gifts to children around the world at Christmas.