Thanks for your query..
Eye sight doesn't worsen by using glasses.
There is a tendency for the refractive error
to increase till 18-20 yrs of age due to general growth.
So one should keep on checking up for eye sight every year.
But 0.25 is too less to prescribe glasses that's why your ophthalmologist must have not prescribed glasses.
You can go for another check up and in case of doubt your son can undergo a dilated refraction
test to confirm the power..
Hope this information helps you..Take care..