I believe earlier replies here are missing the key point of the question: Is it acceptable to begin by saying "one" and then shift to "I". If we are referring to the same person, I would say the answer is "no", unless you are intentionally shifting from the general to the specific.
Your example may fall into that exception. I think the writer is starting out saying what people in primary school do in general, and then he shifts to using himself as an example. That's acceptable. "In primary school one moves outside the home environment. When I was in primary school I met someone from another country for the first time" etc makes sense: a general rule followed by a specific example. That may be the intent of the quoted statements.
But if the intent is that we are talking about the same person, this is wrong because it is confusing. "In primary school one moves outside the home environment. I meet people from other countries for the first time." Does the author mean that in his particular case, this was the first time that he met someone from another country? Or does he mean that no one ever meets someone from another country until he goes to primary school, or that this is where people normally meet those from other countries? The thought becomes confused. If you are still talking about the same person, use the same set of pronouns: he/him/his, I/me/my, you/you/your, etc.
As mgb notes, "one" is consdiered pretty formal these days. Because of the issuing of maintaining point of view, "one" has the catch that when one uses it once in a sentence, one finds one's self forced to repeatedly use "one" until one is sick and tired of it.