I wouldn’t call them a hypocrite because I believe they followed their own advice and were well intentioned in their advice.

In the case of a doctor that tells me smoking is bad even though they smoke, I’m more likely to believe them because they have first hand experience even if they don’t follow their own advice. I don’t think it’s hypocritical to not follow your own advice especially from the point of view that they would follow their own advice if they could and are open about that. In fact there have been numerous smokers in my life who have told me they’re addicted and recommended to me to never start and I did heed their advice.

But that’s not what happened in grade school so I’m not exactly sure what point you are making.