No, a new rate will be applied to only future clients. For clients who book sessions at your original rate you will continue to make that rate.
If you and a current client have agreed on a different hourly rate other than your current one, please go to your "Client List" tab and select *edit* on the rate for that student. From there, you will need to enter the new hourly rate that has been agreed on between you and the client. Once the client confirms the new rate via email, all future sessions will be conducted at that new rate.