Yeah, “workforce” is one of those collective nouns that’s generally treated as a plural. Except when it isn’t.
Similar weirdness is seen in collective nouns like “audience”, for example. You would say, for instance, “The audience is not responding to the jokes”, singular because you’re talking about the behavior of the audience as a unified entity.
But you would also say “The audience have all kept their coats on because the heating system’s not working”, plural because you’re talking about the individual audience members in their individual coats.
And in your example, the question is really about the individuals making up different parts of your workforce demarcated by their educational degrees, so it certainly should be treated as plural.