Apparently, the lesson is not very interesting. ;-)
Can't be studying with Duo then! ;D
What is difference between discipuli and discipulos/discipula?
Discipuli is the plural for male students (disciplus) in the nominative case, I believe.
It's the same sort of difference that exists between "I" and "me", "he" and "him", or "they" and "them" in English. Discipuli and discipulae are nominative ("I"/"he"/"they"), and discipulos and discipulas are accusative ("me"/"him"/"them").
Discipuli is a plural. Discipulos - boy, discipula - girl
Can this also be translated as "The students are sleeping?".
The pronunciation of discipuli is diʃˈʃipuli with the smooth "c"
Not really, because this is meant to be classical Latin, and that pronunciation is ecclesiastial Latin (and probably Italian too, but I don't know that ;)).