Se puede entrar?

Question

While working in a Spanish-speaking school, the kids would say, "Se puede entrar?" to ask if they could enter the class room. The teacher would respond by saying, "Sí, se puede." Why would they use this form? It's like saying, "Can one enter the room?" Is it actually a passive question instead?

Answer

Hola Ruby,
Exactly! you got it right. It is an impersonal sentence formed by "se" + verb conjugated in the 3rd person singular, meaning "one can do something". I can see you have already seen this lesson using modal verbs poder and deber. Here is another general lesson on this if you want to have a look.
I hope this helps.
Saludos
Inma