Tez, I wouldn't think that the school district paid anything for this. I'm sure that this is volunteer work for the celebrities for PR purposes. Get some face time in the news and such.
I'm not so sure of the "face time" motivation here, though, Steve. I think with Sasha it was far more genuinely about her wanting to do it for the kids, having press there wouldn't help that cause, and the way this came out was a gossip site watching Sasha's twitter account. I mean, the initial story in the OP here has the parents reacting well after the fact, possibly only being aware of the reality when asked about it by the news media.
Mostly my own gut feeling. Earlier in this thread there was a list of adult film stars that have made a successful transition (to one degree or another) to more mainstream entertainment. That list was all women. Maybe the list specifically looked at women? I don't know. Anyway, the only male porn start I can think of that has done much mainstream stuff is Ron Jeremy pretty much doing cameos as himself and always as some sort of gag or joke.
Honestly, that's because women are the focus, and in a very real way, controlling and most valued part of the industry. Many of the women, particularly at the higher end of the industry, are in control of most aspects of their career. They can say who they will work with, what they will and won't do, make their own rules, and often move into production and directing. It can be a very real career path when done properly. Yes, there is also the highly negative side as well, but that's another case study. The intelligent ones tend to go more for the former path.
In terms of guys, they get paid less, have less control over who they work with, and so on. Very few have the "staying power" to generate a real career the way the women can, and that will reflect on which side of the gender division the greater number of career-driven people will be on.
Additionally, as Granfire suggests, the women are more "high visibility", which lends itself to a higher chance of using that background to move into mainstream work (again, Sasha is far from the first), whereas the guys would need to start from the bottom again (my, there's a lot of double entendres that just happen to come up when you least expect them, huh?). This lack of visibility would lessen the amount of outcry, really. I mean, if there was someone like Mike Horner was doing the reading, I doubt many would recognise him, or that there would be anyone watching his twitter to reveal it in the first place. And Mike was a lot more prolific, with a much longer career than Sasha...