Schoolies! How could it be anything else? Schoolies are school holidays, when kids tend to let off steam and hoon around, acting like flamin’ galahs.
S could also stand for a snag, or the phrase “straight as the Ocean Road”, which must be pretty straight. Another suggestion from our Aussie consultant was specky. Initially I thought this would mean someone with glasses, as it does here but no. Down under it’s an abbreviation of spectacular, as in, “last night was pretty specky”.