I don't think people are appalled at the idea Cabbage, at least I wasn't. I just don't think that for the amount of time it will take to sort out the order, it will not raise an amount of money proportionate to the time and effort involved. However if you can link the order to the company that makes the school uniform when the school is doing their own order, so they already have the logo and you won't have to pay extra for postage and packaging, then you might have more luck.
I really wasn't trying to spoil your idea, but I do all the clothes ordering for the charity I work with, and it's just not profitable as a fundraiser. If it was I'd be doing it, but the idea is more to get people wearing our logo rather than raising money.
To give you an example, I sell an adults polo shirt with one small embroidered logo on the front for £10. That gives the charity a donation of just over a pound once the cost of the shirt has been paid for. This is only considered profit if I'm doing a big enough order (ie over £100) that we don't have to pay p&p, and it won't profit at all on the first order with a new company if we have had to pay for the artwork set up. Which is why, if you link it into an order the school has to do anyway, you might make a small profit, but I still think it will be disproportionate to the effort involved. That's fine if you want to do it as a nice thing rather than a fundraiser though.
All the adult sized hoodies I sell are at least £25, without any donation to the charity added, but because we use embroidery, it is more expensive than if we used printing or heat transfers.