I do ancient (as per sig) but the question's mark value and most importantly, the answer/response itself is a joke if it were to get 10 marks maybe, let alone above 15/25.
My ancient history teacher marked sections in both the HSC for modern and ancient history before so yeah, he would mark us according to marking criteria. you can get these for past papers from the board of studies as an example
but basically, as people said above, this answer lacks a lot of sophistication and of course the length expected. My teacher says to write like 4-6 pages for a 25 mark section, but also to do that you need to put in a lot of detail. My teacher says, for the 'extended response' q's you need to put a lot of detail. Now what he means and what I mean by that, is even though the question doesn't explicitly say to use sources (e.g. modern/ancient primary & secondary sources), such as this question you will still need to!
However one thing I want to say is that we're not doing this section for the HSC, so I don't know what info you need for this answer to get a true 25/25 in my opinion. Now if my teacher was marking this question, and if it were out of 10, according to the marking criteria table, this might get at least an 8 out of 10, as it is fairly detailed and is logical, referring to the question with examples. I can't say 10 exactly as I'm not studying this module so I don't know the content.
BUT BUT BUT for a 25 marker this is where it becomes a LOT different. Now, my teacher marks 25 markers/extended response somewhat 'essay' type questions with this marking criteria: how much sources you have put into your response. Now this student has made 0 references to sources in this question which is kind of mark suicide for especially a 25 marker. If you talk about just what is required w/o mention of any sources/historians/archaeologists/evidence, I suppose you can get a maximum of 12, and if you have answered very detailed with still no references to evidence, at best maybe a 14 or 15. Sources, evidence, are really important. My teacher says if you don't, you just say goodbye to good marks. So if you could've got 10/10, without any sources or evidence your answer is easily a 6 or 5. Also you need to evaluate the evidence in the way that supports your argument, as well as state differences in opinion between different historians (just to say there are different interpretations/views like in this case, how a colony was established). So you can't just be like Historian A says this, Historian B says that as you are just saying not evaluating, and that would get you a 21/25 at best. So to get 25/25 marks, you need to talk really detailed, and as I said, integrate sources/evidence into your response (both supporting and opposing, and both modern/ancient historians and evidence) to support how a colony was established.
Anyhow I still think and will agree your teacher is quite biased and also marking/setting up your whole class wrong for ancient history, especially for the HSC. but like as someth1ng said, go up to your deputy, then principal then board of studies. another good thing to do, is like talk to your whole class, just like go 'hey do you think our teacher is being dodgy?' Then show them what you think by looking at marking criteria from past HSC exams on the BOS website, compare it to that girl's 25/25 response and say like how your teacher marks is way too lenient and wrong for a HSC standard and just gage their response. Say you are doing it for the better of them, like if you let them be, that girl will only be getting like 60% in ancient in the HSC and that it will bring your whole class down. Also if you can, get some actual assessment tasks from other schools doing ancient history. I can give you mine if you'd like, so you can actually compare and see 'this is how it's supposed to be marked'. Also like if you can, complain as a class (as much as possible, with as many students who are willing) to deputy, then if it doesn't work out, then to principal, then a whole class complain to BOS, so it will be a lot convincing.
Yeah and also as someth1ng said, try making your school do student numbers system, but also as he said, naming and shaming and most of all, not being afraid to raise issues with a higher hierarchy if the previous one doesn't work will only get you further. If you can, try going to another school (as many as you can), as in write a letter to their ancient history teachers and get them to evaluate how your teacher marks in relation to HSC so show them copies of your assessment task and a couple copies of student responses with varying marks. So get them to write back to you about it, so you have even more evidence to support your statement that you feel your teacher is pretty inadequate. I think a private school or a notable public school would be best (esp. selectives). Also get their assessment tasks with marking criteria/exemplar responses of them so you can go complain back at school/BOS with the rest of your class a lot better as you can compare the discrepancies between fair/unfair. Best of luck with your complaint