Is your son getting any indication why these professors are telling him “try again next quarter” or “no”? In his freshman year, and even now in the first semester of his sophomore year, it could be that he’s just asking too early. In science fields - especially at large universities where labs are primarily supported by graduate students and postdocs - sometimes labs won’t take on students before junior year, because they don’t have the skills yet to be useful in the lab.
I would usually advise deferring to the advice of professors in one’s field, but that professor’s advice sounds…weird. He may be right in that he needs to go elsewhere to get research experience, but there are definitely more places to go than moving all the way to Australia to get it done. There are post-college programs here in the States that would expose him to research.
But the most important part of the statement is " since he won’t be able to get any research opportunities at his current school." Again I ask - why is that? He’s been getting that message consistently from several professors in his department, and your son should be asking professors WHY that is, because only that’s going help him decide what to do next. If it’s simply that he’s too junior, all he’s got to do is wait a semester. But if it’s that there are no opportunities at his university, then transferring or seeking outside opportunities over the summer and after college may be the right approach.
I will say that I don’t agree with the advice that the grades are much more important. For PhD programs, research experience is pretty much the most important thing, and many (dare I say most) PhD programs will take a student with a 3.5 and solid research experience over a student with a 3.8 and no experience. Students can do really well in school but dislike research or just not be good at it, and doctoral programs like to know that their students have some sense of what they’re getting themselves into (and also, that they’ll be useful in the lab).