I thank you again for your quick answer.
We have the staff parent import module and I have used it to import the bulk of our users, when I set up Rosario.
It is the users that get entered piecemeal during the year, and especially in the first two months, who I'm concerned about.
Also, just for the sake of it. Using the import module does not lower the number of iterations. If I have to fill a spreadsheet with 200 users, I still have to make 200 records, thus doing the same thing as many times. I only consolidate the amount of steps I have to take, and mitigate some errors. But that's academic here, i think.
I'll have a closer look at the permission option.
As for your last remark, I believe that for most schools, except those in adult education, parents make up the largest number, which would be a reason in itself, as far as I'm concerned. But yes, opinions differ.
Mine, however, is that it is always best practise to default to the least compromising option.