Emarketing can be such a powerful tool but so easily abused. The gains you receive may quickly be reverse by its overuse or misuse. Personally, I think that on an ethical level, this is dubious. The school obviously stands to profit by selling their list to the third party. But the point is that people had to opt out, and it gave them 2 days to do so, some people would not have even got the message by the time their details had been sold onwards.
When people give you their contact information, they are placing trust into your hands. Don't abuse it by handing it on to someone else for a quick buck.
The problem is, that the list becomes one of such a lower quality. People who receive this message that has been passed on without consent will have a lower propensity to purchase the products of that company than they otherwise would have. They may infact even be annoyed to receive these messages.
What they could have done was to write a message saying "this organisation supports the school, they have some great products and a special offer for people who respond to this message, you can opt in to receive useful updates on ... topics and frequent special offers." The people who were already predisposed to purchase those products would have loved it. The other would have ignored it, but not been annoyed when they encountered this brand in the future.
