I want to say that math improves the 'ability to reason' and 'elasticity of mind'. This is what I would say in my language (Italian).
After a Google search I see that 'ability of reason' is an existing periphrasis and instead of elasticity of mind I find 'mental agility'. I never heard anyone use these words in English, so I was wondering if they are not correct in this context. Is there something else you say instead to express the same concept? What do school teachers tell students?