Further numbers:

Canada wide, total school enrollment (elementary and secondary) has been between 5Mn and 5.7Mn in all school types for the last 20 years, undulating up and down.

Total workers employed by the education industry (codes 61 and 611) over the same period has increased form 981k to 1,393k.

So about 40% more people in the industry for 14% more school age students.

So what's going on here? I can think of a few possible explanations:

1. An increase in part time work. Number of workers go up, but total hours of work go down. Edit: full time has actually been increasing as a percentage. Perhaps just educators are getting a part time squeeze?

2. Education includes post-secondary. Since post-secondary has become a lucrative business, employees are more likely to favour working there for more compensation.

3. Since we've sold the narrative of post-secondary being a workforce gateway, the number of people going to post-secondary schools, poaching educators from grade schools. Related to point 2, this poaching is likely to be effective. (1.5Mn to 2.1Mn over the last 2 decades).

4. Increase in overhead. I assume IT requirements have ballooned, but dated buildings may also increase janitorial requirements.

Even with post-secondary included, total students are only up 20%. Teaching has probably become more efficient with IT and other tools. Administration has certainly become more efficient.

All numbers from Statscan, rounding errors abound.

We’ve never had as many working age people as we do today

In absolute numbers that is true, but the workforce has declined relative to the size of the population. If there are two people and one of them is in the workforce, that might be okay. If the population then grows to 100 people and now two people are in the workforce, you've doubled the workforce!, but you're bound to have a bad time.

The questions are “why can’t we attract workers into X fields”

Because the workforce has shrunk, relative to the need for workers. A larger population needs more productive capacity.

but more national, question of “why does a worker, that produces more than ever, have less purchasing power than ever?”

Because we reached peak worker productivity a long, long time ago. Overall productivity is up only because capital has picked up the slack.

Funny thing is, once upon a time we encouraged our youth into university research labs to develop new capital which they could capitalize on, promising a higher income on the back of the productivity of the capital. Curiously, we heard the university part, and we heard the higher income part, but glazed over the rest. For some reason that message turned into people thinking they should go to university to get a job where they can be no more productive than any other person has ever been. And, unsurprisingly, incomes have held stagnant for that segment of the population, to which they now act like we have no idea what's going on...