Can you walk me through this?
A pensioner is a millionaire, say, and gets a free bus pass (OAPs in the UK are entitle to a travel pass regardless of their financial position). A school child wants to get to school but can't afford the bus so has to walk 2.9 miles each way to school.
How is it not ageism that based only on age the pensioner gets a bus pass and the child doesn't? You can argue that the ageism is justified as the general principle is sound (for example) but it's still ageism - discrimination based solely on the age of the subjects.
The child could be disabled, they still wouldn't necessarily qualify for a bus pass.