As someone who has been in the "Ed Bis" since 1984, I would surmise from looking at the PADI curricula and how they are designed, that the PADI courses use what is called "Mastery Learning." From Wikipedia:
"Mastery Learning (or as it was initially called, learning for mastery) is an instructional strategy and educational philosophy, first formally proposed by
Benjamin S. Bloom in 1968. Mastery Learning maintains that students must achieve a level of mastery (i.e. 90% on a knowledge test) in prerequisite knowledge before moving forward to learn subsequent information. If a student does not achieve mastery on the test, they are given additional support in learning and reviewing the information, then tested again. This cycle will continue until the learner accomplishes mastery, and may move on to the next stage.
Mastery learning methods suggest that the focus of instruction should be the time required for different students to learn the same material and achieve the same level of mastery. This is very much in contrast with classic models of teaching, which focus more on differences in students' ability and where all students are given approximately the same amount of time to learn and the same set of instructions."
It seems as though you should have been given more opportunities to master the skills and that your time required might be longer than other students which should have been OK. It has taken my wife and me more than the stated number of dives to perform all of the required skills in some of the PADI classes, so we just did extra dives (that we paid for additional). We recently just passed the Rescue Diver course and it was tough for us. (I thought they were going to have to rescue US instead of the person playing the victim
). I do not understand why you must wait 6 months before doing it again. Is that what the instructor said or is it entirely because of your own situation? You might ask the shop for a different instructor if that is possible. Good luck to you.