LSAT/ Law School Questions

[Riverman]

Im taking the test Saturday. I have been told that if you think you did poorly you can cancel your score and law schools will never know you took it. Is this true, how long after do you have to do this, and how does one go about canceling a score?

Also, is it true that applying this late will hurt my chances of getting into a good school? My practice tests are between 165-170 so I'm gonna apply to some good schools