Good question. What exactly is your definition of working class? occupation and salarly? If you're referring to manually labors and skilled industrial workers we are on the same page.
Caveat: for the skilled industrial workers and skilled manually laborers who can't get there jobs replaced by a robot and who may have a well paying job there may be no advantage to switching. That's probably under 5% of the group though. Now for the other 95% huge advantage And you ask what would happen to the stem field...well first there is a huge shortage of people in stem. The reason being the barrier to entry is set very high. The academic rigor one must complete to enter the field is High. For many that barrier is passing hard biology, chemistry, coding and math courses so many people won't make it anyway.
But if they all do hypothetically, then they will Fill the shortage of stem qualified people we have.