There’s a shortage of teachers prepared to teach in science and math and other technical fields and there’s a shortage of teachers with special education training. This has been true for decades and hasn’t gotten noticeably better.
In the private sector, if you can’t fill staff slots for particular specialties you offer to pay more money. Not so in public education. This too has been true for decades and hasn’t gotten noticeably better.
Here’s a picture from a recent paper by Dan Goldhaber’s shop. The data for “difficult-to-fill” comes from the Schools and Staffing Survey and is measured by responses from schools that vacancies were “very difficult” to fill or that the school “could not fill vacancy.” Not only are the blue and red bars high, they’ve been that way for a couple of decades.