[randomdata]

Although, there is a fifth state in your example: When you are not in class. Which is different to an empty set that implies nothingness. When it comes to age, 0 being birth works well because there is truly is nothingness (from your perspective) before birth. When counting from 1 there is suggestion that there are variables that aren't worth speaking of because they are obvious.

[goatlover]

Assuming there is nothingness for the fetus the entire nine months in the womb. For that matter, I can't recall being younger than four, so it's all nothingness before then.

[randomdata]

Not really. Perspective isn't scientific and often cultural. Koreans, for example, famously have a different take and use a different counting systems to accommodate.

I am assuming that the reader is biased towards the average HN user. That won't always work for everyone who will come across my comment, but close enough for an unpaid contribution. I'm not about to write a novel to make sure I catch every edge case.