Its performance on riddles has always seemed mostly irrelevant to me. Want to know if models can program? Ask them to program, and give them access to a compiler (they can now).
Want to know if it can do PhD level questions? Ask it questions a PhD (or at least grad student) would ask it.
They also reflect the tone and knowledge of the user and question. Ask it about your cat's astrological sign and you get emojis and short sentences in list form. Ask it why large atoms are unstable and you get paragraphs with larger vocabulary. Use jargon and it becomes more of an expert. etc.
If you can tell when your students use it, presumably you mean they're just copying whatever, which just sounds like that student doesn't know what they're doing or is being lazy. That doesn't mean the model isn't capable; it means an incapable person won't know what they'd want to ask of it.
Additionally, even for similar prompts, my experience is that the models for professional use (e.g. gpt-codex) take on a much more professional tone and level of pragmatism (e.g. no sycophancy) than models for general consumer entertainment use (e.g. chatgpt).
I use AI for coding, but not for anything involving writing text, it's just horrendous at it. It just spews verbose slop, devoid of meaning, original thought or nuanced critique.
> That doesn't mean the model isn't capable; it means an incapable person won't know what they'd want to ask of it.
So it's user error again then, eh? PhD experts are able to help even "incapable" students, that's often a big part of their job.