Ok I see now. You've actually managed to do a heck of a lot by simply following the instructions. I think that, whilst it is really very admirable that you achieved what you have, it is really the wrong angle to approach it from... unless you're planning on taking over the IT department.
You're correct that DNN assumes people are professionals.. not just as designers, but also as systems engineers. There is a level that DNN pitches itself at where people do not have to be IT or design professionals, and that is at the actual user end of the application. I feel that is where you chould be focussing your efforts in the long run. (You're also a victim of the confused communications here on the DNN website, but that's another story)
The school/s should really be engaging the services of a DNN professional to install and configure portal systems for the teachers to use. You've (again, admirably) taken on all the tasks of the IT systems engineer and a skin developer in order to get DNN running locally... and although it works, it is not something that one can simply tansfer to another IT system by FTP in the manner of the old fashioned static websites. The school may not even use IIS, and if they did, the chance that they would allow someone to install a web application like DNN on it is pretty remote - at least it would be if they had good operating procedures.
I would first check with the IT staff whether or not they would set up a DNN portal system for the school, and then carry out your work on that. Alternatively, and this is useful in situations where there is no useful access to IT services, and/or too many security policies in the way, you can always get a hosted copy of DNN outside the school.
However, for the best management of web services for teachers and other working professionals, I would really suggest purchasing professional IT services or making use of any that you have access to throught the school. DNN and any other system like it will waste months of your time unless you plan on becoming a DNN service provider yourself. There is always a service provider with a price to match almost any budget.
Hope that helps a little
Rob