IF (big if) there's actually anything to this rumour and IF (big if) someone just getting a head teacher's award was in danger then by now it would be more than just a rumour - think about it, other pupils have been dealing with this head for years. Female pupils will have received the head teacher's award for roughly half of the weeks so far this term, and all of last year and for years before that, and if they weren't fine then by now that teacher would not be in post any more.
I know how horrible it is to be worried about something with everyone dismissing your worries. The less other people seem to worry, the more worried you feel because all the weight of responsibility for being careful seems to fall on to your shoulders. Other people dismissing a worry is sometimes the opposite of reassuring, it makes you feel even more that you're on your own with the job of making sure everything is safe.
However, even if you were to move your daughter, you should remember that statistically there's probably a dodgy teacher in a few of the schools local to you, including the one you wish she had gone to, and you're highly unlikely to ever know who it is, and also it's very unlikely statistically that your child would be affected even if it's in her school. Many predators go unidentified for years so you're not automatically safe in a school there are no rumours about, equally when a predator is identified their interactions haven't usually been with more than a tiny tiny minority of their charges.
The best thing you can do to help protect your daughter from dodgy or predatory people is to teach her how to handle situations in which she feels uncomfortable - things like knowing that there are situations in which being polite is not the most important thing, so for instance if she feels uncomfortable it's fine to just walk away without saying another word.
You can't do it for her by keeping her away from places there have ever been rumours about, because apart from anything else a school not having had rumours about it is no guarantee that every single person there is fine, and it would be dangerous to assume that it was.
It isn't just down to you to worry about this - you can relax and leave some of this up to other people, really you can. The school is full of other adults and children are rarely on their own with any of them. A big secondary school with children who are verbal (and so able to report back to their parents anything that happens) is not the same thing as a much younger or preverbal child being on their own for several hours with a single babysitter. (If you'd heard a rumour like that about someone you were using as a babysitter, it would make more sense to worry about it, but that's not the situation you're in.)