The Upper School choral program includes the following ensembles:
- The Mahertians: A co-ed singing group comprised of Brunswick and Greenwich Academy students.
- The Twelve: A select group of 12 singers who meet twice a week.
- The Men of Brunswick: A male a cappella group that draws from the Mahertians and the Twelve. The Men of Brunswick are exposed to a wide range of intricate harmonies from be-bop to rock.
In addition to these ensembles, smaller quartets and octets are encouraged to rehearse and perform tunes of their choice. These groups perform at numerous school functions, which include the open house for parents, holiday and spring concerts, and graduation. In addition, many perform at community venues during the year.