Of course that I agree with the concepts firstly mentioned in this thread, but things are not so absolute.
Some thoughts from a newbie instructor.
1) Not everything is for everyone.
Cert agencies are proposing that diving is for everyone, so the base is bigger and more people could start diving. I do not agree with this. I see frequently students that come to a basic diving class and they have panic to the water or panic to be in a pool and their feet not touching the bottom. It's quite hard to start from that point. What are you doing here if you are panicking in the water ? Peer pressure ?
2) Time is money. Money is scarce.
Many of us work in this industry for our own pleasure and as a hobby.
You should advocate time to a student that has problems to learn a skill, but where is the limit ? a full pool session, a day, a week, a month ? Pool time is expensive.
I've seen many times students that start a course, finish it and does not pass the pool exam, just because they cannot do the skills. And they just judge that those skills are not important to dive. We correct the skills one, two, three times, but no answer, no better. It seems that what we say goes from one ear to the other without staying in between.
3) Classroom sessions
We always say read the book and watch the videos. The book is part of the student's materials and part of the course cost, the videos are free in Youtube. Only a few read part of the book. Even less watch the videos.
When I started my OWD course I read the full book the first day and read it several times.
Today every thing should came light, with minimal effort. Otherwise "this is not for me" is the typical phrase.
I see students that try a skill, they cannot do it, for a million reasons, all classical, and they quit. "This is not for me", "Today is not my day". Some even get out of the pool, take they things and leave, without a word. Sometimes this could have a reason, but the tendency is everyday more and more.
We always say that diving is a risky sport. The sea gives no second chance. The sea does not ask who you are and where you learnt. Diving is very safe, but things can go wrong and the diver should be ready to face the situation. The skills learnt not only are for safe diving but also to cope with problematic situations. At OWD level, only soft problems. This makes no difference.
And of course that I see students that are very good, and students that are normal and they learn at the correct pace.
Teaching/learning to dive is a two person relationship. Both are responsible for learning.