Translation:They left from here, however they did not go to school.
This (English) sentence is a bit of a mess to my ears, though not grammatically incorrect. I was marked wrong on this for writing "...tidak bersekolah" which I get is semantically different from "tidak ke sekolah", but without context is more likely to be the translation of "Did not go to school"
agree that the sentence in english, while grammatical, just doesn't sound like something you'd actually say. something like: 'they already left to go to...' rather than 'but not go to...' sounds more natural. however maybe in indonesian this is not an unusual sentence structure?
it also doesn't accept my translation of 'pergi' as 'leave', which is acceptable elsewhere in the course.
finally, i'm becoming a little confused about the use of 'namun' versus '(te)tapi'...
it all depends on context in Indonesia, as they don't really have tenses. The same sentence can mean past if you're telling a story about them, present - for example if they are still visible so it's clear that they are still going - or even future (if they are still sitting here but getting ready to go)
This sentence should use "but" instead of "however". The conjunction "however" should be used at the start of a sentence before a coma or in the middle of a sentence after a semicolon. The English translation just sounds off.
I think the "namun" in this sentence should be translated to "tetapi" instead. Indonesian words are rather fluid in meaning.