Hi, I wouldn't put that I work for a tutoring agency. Go free lance on your own back but be careful if your employers find out there may be something in your employment contract that doesn't allow you to do the same line of work while employed by them. They then see an employer as a competitor.
I wold only mention agencies if people can lookup your history on the site.
Making your own site on a free host like Blogger.com for the ad to go to would be a big plus, investing $12/year on a custom domain name would make it more professional looking.
I don't think you should mention the agency by name.
Say something to the effect that you have worked for one of the leading, premier agencies.
Probably...better just to give the impression that you are independent and experienced
I am putting an advert on a website for tutoring. At the moment I work for a tutoring agency. I want to put that I work for this agency (because it's very good and also it sounds like I have experience), but then I thought maybe that isn't a good idea? Will it just make people go to the agency instead of me?