Sure, but I think you should compare the incentives between the two situations. A teacher doesn't have a real incentive to hand off your child to a stranger.

Sure, but I think you should compare the incentives between the two situations. A teacher doesn't have a real incentive to hand off your child to a stranger. A company holding a large amount of user data has the opportunity to make millions or billions of dollars if they are allowed to sell it as they please. And they would likely do everything in their power to do so if they thought they could get away with it. That is why I think it's such a slippery slope that we should avoid all together.