Fact: School can prevent you from doing a course.
Fact: They can only stop you from doing a course, if a class is full (filled to capacity), according to legislation and bylaws (for public schools), or regulations (private/religious schools).
Fact: Schools are (obviously) allowed to give places according to Year 11 marks. So if there are only two teachers teaching MX2, and say, a max of 25 students per class, they will offer it to the top 50 students.
Fact: If anyone rejects their offer, then the 51st student gets the offer.
etc. etc.
Last Fact: You can only appeal if: 1. The class is not full according to regulations/bylaws. 2. If the class is not full, check with people who were ranked above you. If they accepted, chances are, you just missed out. For instance, if you're 58th, and only 7 people from the original 50 declined their offer, and the subsequent 7 students all accepted, you're pretty much up shit creek with regards to getting into MX2.
Also, I laughed at how you said 'it's always been a dream of yours to do MX2. Really? A dream to do MX2? People dream of becoming doctors and Prime Ministers and Presidents. Not of doing MX2.