Rescue is the first class I want my students to take after Open Water. Or at a minimum my rescue skills workshop that is basically the rescue class with a lot of emphasis on prevention and responding as a team rather than as an individual.
Rescue should be done before AOW and depending on the Intro to Tech class you are taking, certainly before it. My ITT class is 6 dives and includes classroom and pool sessions. Rescue helps to identify those portions of ITT that you may want to pay special attention to before you even get in the water. For many people ITT is the first time they'll experience doubles, carrying a stage, sidemount, etc. Rescue will help to identify those areas where the additional gear may require you to adjust your expectations and do a self-evaluation.
Are you ready for the additional weight of doubles, the extra task loading, the extra gear? Do you really trust your buddies and your ability to assist each other?
Rescue skills used to be in every OW class. They got dropped in order to increase output and profits by some agencies. Other agencies and instructors still include them in the open water class.