First of all, what do you mean by a diving school? Are you talking about agencies? Are you talking about training agencies? Local shops that teach diving? Large scale programs that take divers all the way through instructor?
If you are talking about agencies, like PADI, SSI, NAUI, SDI, etc., then no, that would not be possible. That is because those agencies do not teach diving themselves. They set standards by which other people teach diving. If you go to a shop that teaches according to the PADI system, it is the local shop that does the teaching and charges the money for it, not the agency.
If you are talking about local shops, then it would in theory be possible to make a site that compares them, but there are many thousands of such shops around the world. Like any business, they go in and out of existence, and they change their prices in response to local demands.
The same is true of the big operations, although there are fewer of them.
Finally, as for ratings, there is no universal rating system for shops and agencies. Different people have their own opinions, but there is no standard by which agencies or shops can be judged.