Better worded topic sentence: The prejudices surrounding ethnolects suggest that individuals are judged based on their way/means of speaking.
Australia has seen an increase in number of language groups over the years due to factors such as globalisation. In Melbourne alone there are 215 different languages spoken. Ethnolects are marked by distinct lexical and phonetic/phonological features such as in German ethnolects which contain phonological features such as voiceless stops in final position.
Two things. The increase in number of language groups doesn't really follow-up on your point that there are prejudices surrounding ethnolects. If anything, since there are so many languages spoken, wouldn't that be an indication that Australians are non-judgemental about different cultures/languages/ethnolects? You're also better bringing in stats about ethnolects rather than languages. Also, you're not required to explain what an ethnolect is since the examiner knows (write like the reader has knowledge about EngLang to a year 12 standard) but I guess you're showing the examiner you know what an ethnolect is.
'In 1985, an accent variation known as ‘ethnic broad’ established from Greek and Italian English speakers was highly prevalent in Sydney. People who spoke this accent variation were stigmatised as uneducated and of a lower social class and this covert prejudice lead to children to alter
there please spell 'their' correctly accent to
fit in conform with their
school peers
at school.'
Surely you can bring in a more up-to-date example? A lot can change from 1985... also watch your spelling and try keep your sentences formal (conform instead of fit in)
'
insert linking word like thereforeThe prejudices and stigma surrounding ethnolects illustrates how individuals can be judged on the way they speak. '
Overall this paragraph was a bit on the shorter side and you probably could have fit a more comprehensive example, and demonstrated how people are prejudiced based on their accent based on an actual event in 2018. Also, I'm not sure if 'covert' is the correct word to use to describe the prejudice, otherwise speakers would probably not feel obliged to change their accent.
This is just my quick feedback, hope it was helpful!

Of course, you could also disagree and say that people aren't judged lol