I have been trying to translate 'school was hard because everyone was born here (australia)' and am not sure if this is the right grammar or not.
Grammatically speaking, this is a fairly simple sentence, and your understanding of the sentence is basically OK. But it's a little difficult to make sense of it without proper context. When you ask about the interpretation of a sentence, please don't forget to include some context. Usually a few surrounding sentences will greatly help.
誰もがここで生まれたので just means "because everyone was bone here". What 誰も actually refers to depends on the context. It may be "everyone in my village", "everyone in my class", etc.
学校は大変でした is technically ambiguous, and many sentences are ambiguous without proper context in topic-prominent languages like Japanese. Roughly speaking, this sentence can mean:
- the school had hard time (because of these people)
- these people (may or may not include the speaker) had a hard time about something related to school
- I had hard time at school
From the context you provided, I think the sentence means "Everyone in my class but me was born here in Australia, so I had hard time at school (due to language problems, etc)".