Social status (in my own words) is the idea that a person has a relative social worth in a certain context. For example in a class room a teacher has a high social status and therefore must be listened to. On the other hand, if that same teacher was stopped by the police for speeding, they would not have a relatively low status compared to the police officer and should therefore listen to the police officer.
Basically you are expected to treat some people with more deference than others based upon status signifiers like what role they have and what clothing they are wearing or how they speak or act towards to you.
I guess you could say it is a widely held belief that some people are better or more important than others.
How would you approach explaining that idea to a child? When is age would be too soon? When would it make sense to explain that it is a person's social status is not always justified (i.e cops, bosses, parents)? Traditionally, I guess they would learn it by trial and error but I don't necessarily think they would learn the idea that it is often abused to control others in a school setting since authority figures generally don't want others questioning them.