Self teaching a higher

Next year I am going to be studying 3 additional highers out with school. Specifically business management, administration and IT & italian.
If anyone has self taught a higher could you give me advice about how you did it.
How did you do the unit assessments?
Also if anyone has done business how did you prepare for the assignment?
I probably will not be getting any help from my school as they probably wouldn't even let me do one additional higher let alone three. No one has ever done more than five highers at my school therefore I will likely be sitting the highers at a college as an external candidate.

Hi
I haven't done any of the subjects that you are interested in, but I am self teaching higher human biology this year. My school were relatively supportive in that I just speak to the biology teacher and do the unit assessments whenever the classes are doing them. And for the assignment, I did all of the preparatory work at home and did the write up during lunchtimes/RE lessons.
You could try and have a similar arrangement with your school if they teach the subjects you're interested in? It will depend on the individual subjects though- some (music as an example-but I'm sure there will be others) will insist that you are in class to be able to tick off outcomes/ complete coursework, so check with individual teachers/departments if they might be willing to let you do this. If they do insist that you are in class, it is likely that a college will also insist that you attend a course.
If you do need to go to college, send them an email outlining your situation and ask them what they would recommend and whether they would require your attendance.
Out of interest, why is it you want to do so many highers?
Hope this is of some help

Thank you, that is helpful.
I want to do additional highers because I think I would be capable. For some of my subjects that I am doing at the moment for national 5's, I have done the higher past papers and could have done the higher this year and achieved an A so I would probably find five highers too easy. I also enjoy learning so I think I genuinely would enjoy it as I would be studying subjects I am very interested in and very good at. I also want to go to university in England, hopefully Cambridge.