The school rapidly outgrew the single house, leading to the main building of the present day college by 1884.

During the world wars, the school was evacuated to Chester (1915) and Courteenhall in Northamptonshire (1940), seat of Sir Herewood Wake, because of its position on the South-East coast.

Later in the school's existence, girls were admitted, and the current mix of sexes is now roughly equal.

In 1930, Richard Maunsell designed for the Southern Railway a fleet of 40 "Schools Class" locomotives one of which was named St Lawrence.

As late as 1958 the St Lawrence Loco (BR 30934) was attached to the School Train departing from Ramsgate.

In January 2013, Mark Aitken retired his post of Headmaster and was succeeded by Antony Spencer.