Over time enrollment fell, and the school was frequently threatened with closure.

In the 1980s it became one of a number of Ottawa area alternative schools focused on independent and unstructured learning.

In 1991, the City of Ottawa awarded the building heritage status, ensuring that the exterior structure could not be demolished as had been done with Churchill and Lady Evelyn schools when the city rebuilt and thus modernized both schools in the early 1990s.

In 1991, the Grade 6 students at Crichton School met with then city mayor Jacquelin Holzman to protest the city's planned consideration for the expansion of the Vanier Parkway through New Edinburgh over to Hull, Quebec.

In 1998, the Grade 6 students at Crichton School participated in the 25th Anniversary celebrations for the Lester B. Pearson Building, used by Foreign Affairs Canada.