It was established in 1714 by voluntary subscription for the clothing and education of a limited number of boys born within Mile End Old Town.

The inspectors also found that the school segregated boys from girls outside of lessons, and felt that it failed to do enough to keep students safe from the risks posed by extremism.

In June 2020, during the global George Floyd protests, it was announced the school would be changing its name to remove the reference to Sir John Cass due to his connections with the slave trade.

[13] In September 2023, the school became the only one in the United Kingdom to completely close due to concerns about reinforced autoclaved aerated concrete (RAAC).

Although the school is run by the Church of England, ninety per cent of its pupils come from ethnic Bangladeshi, mainly Muslim backgrounds.