In 1890 the school moved location to North Hill, Plymouth (now the site of St Matthias church hall[6]), moving in 1900 to larger premises at Mount House, Approach Road, Plymouth (the birthplace of Miss Tubbs).

Plymouth was heavily bombed in World War II and the school relocated to a 50-acre site at Mount Tavy in 1940.

Mount House School became co-educational in 1996 with a pre-prep established for 3- to 7-year-olds ten years later.

[7] The school has a Combined Cadet Force, and runs the Duke of Edinburgh Award scheme.

[8] In 2016 the school built a 50-metre, 8-lane Olympic Legacy swimming pool, financed in part by Sport England and the National Lottery (United Kingdom).