In your country and culture, what time would be acceptable to arrive for a business meeting scheduled at 10am, or a language lesson scheduled at 2pm? Where would you put your culture on a "punctuality" scale? Must you arrive at the exact time?
From one culture to another, the notion of time, including everything relying on that notion, varies widely: punctuality, respecting work hours and meeting times... Must you call ahead or apologise if you are late, if you cannot make it to a meeting, even if it's informal? Are people always in a hurry? What value is placed on a slow pace? Can you "take your time?"
Western francophones are punctual for meetings of a professional, medical, and educational nature. It is frowned upon to waste other people's time by being late. This rule is take even more seriously with regards to public transportation - like high-speed trains, for instance - where every second counts.
As a general rule, you call ahead to let people know if you're going to be late to a meeting. However, in France, for informal meetings amongst friends, it is not considered rude to arrive late: this is called the fifteen minute courtesy.