Brett is the Director of the Architectural Association School of Architecture, including the AA Public Programme and AA Publications. In 2008 Brett founded the AA Visiting School, an international programme of global design workshops that have enrolled more than a thousand visiting students all over the world.

He is partner of desArchLab, an architectural office in London, and has taught and lectured at schools throughout the world. He is the editor of various books such as SUPERCRITICAL: PETER EISENMAN MEETS REM KOOLHAAS (2009) and the series editor of ARCHITECTURAL WORDS, critical writings in modern and contemporary architecture; and AA AGENDAS, a series documenting the work of the AA School.