I think I remember a similar thing being critiqued by a stuffy grammarian once. They insisted that the right form with "in order" in such a case would be "in order that scientists might analyse them." Never did get a proper explanation why.
In everyday English, it's fine, just a little awkward. For starters, "in order" is redundant. "...for scientists to analyse them" is less formal than using in order that, but it is perfectly good everyday English. Indeed, the fact it is less formal is part of why it is awkward quite aside from the redundancy. It may not even be necessary to explicitly indicate that this is a matter of purpose - "...where scientists analyse them" does perfectly well.
To be absolutely rigorous, I suspect the example your teacher took exception to might be mixing different constructions. I understand that "for [subject] to [verb] them" is an adverbial of purpose, albeit an informal one. So is "in order that [subject] may/might [verb] them", but it is a different one (authorities seem to disagree on the right circumstances to use may vs might). I can see that a strict grammarian might object to mixing them.