Hi Dej,
RSV is tough for young babies as they are unable to cough properly to release phlegm etc. Once they get older and start moving around they tend to handle illness better.
You will find that he may get it again and you won't even realise it.
The fact is that there are some kids who get really sick and others that don't seem to have as many issues when they get sick.
It is perfectly normal for all kids to get 10 mini colds per year where they will have a slight runny nose etc and this can occur even if they are not in school, but yes kids do tend to pass germs around at school.
It is important that you discuss the school policy when it comes to sick kids. While it is understandable that parents have to work, it is unfair to send your sick kid to school. When they are toddlers it isn't as serious, but the school should be really strick when it comes to babies.
I must just state though that Dylan had RSV at 5 months and he seemed a bit chesty but not really sick and he didnt' have a fever so I had no idea he had RSV and sent him to school. He was the only baby though so no risk.