Here's the gap that actually matters, and it isn't the one most parents ask about. People usually ask a tutor about years of experience or subject credentials. What actually separates a full-time teacher from a part-time one tends to show up somewhere else: in pacing, in how precisely they can name what's wrong with a specific piece of work, and in whether they can sustain the job at all once the fourth term of the year rolls around.
I've taught alongside people early in their tutoring careers who were bright and genuinely good with students, and alongside people who've done this full-time for well over a decade. The content knowledge gap between the two groups is usually smaller than you'd expect.
The pacing gap is the first thing you notice. Someone teaching full-time has stood in front of enough different students, at enough different speeds, to have a real feel for when to slow down and when slowing down is just indulging confusion. That instinct doesn't come from knowing the subject better. It comes from watching the same explanation land for one student and completely miss for the next, dozens of times, and having had to adjust in real time rather than in hindsight afterwards.
Anyone can tell a student something is wrong. Saying precisely why, for this student, takes years to build.
The bigger gap shows up in feedback, though. What takes longer to build is the ability to say precisely why something is wrong in a way that's specific to this student's actual error, rather than a generic correction that happens to be true of most students. That specificity is a pattern-recognition skill. It gets built by seeing the same category of mistake made by dozens of different students in dozens of different ways, until a new mistake can be placed within a family you already understand, instead of being met as if you're seeing it for the first time.
There's something less flattering worth admitting too: teaching, done properly, is tiring in a specific way that has nothing to do with hours worked. That's different from knowing the material cold. It means holding a room's attention while reading who's actually following and who's just nodding along, then adjusting the lesson mid-stream when the plan clearly isn't working. That specific kind of effort is hard to sustain as a side activity squeezed around something else, not because people with other commitments don't care, but because the muscle needs regular use to stay sharp, the same as any other skill.
It's worth being specific about the part-time undergraduate route in particular, because it's the most common one families weigh on price. A current university student who scored well in the subject can absolutely help, and the rate is usually lower for a reason. But the risks are structural, not personal. Their own degree comes first, so when their exam period collides with your child's, your child is the one who gets deprioritised, and it tends to happen at the worst point in the year. Continuity is fragile: a graduating tutor, an internship, or an exchange semester can end the arrangement mid-syllabus, and a JC1 student who has to switch tutors partway through JC2 loses the one person who actually knew their writing. They're often learning to teach on your child's time, which is fine when the student mainly needs content explained and expensive when the student needs a specific weakness diagnosed. And a solo private tutor has no colleague to moderate against, no second opinion on whether a script really is at the standard they think it is. None of this makes undergraduate tutors a bad choice outright. It just means the low headline rate is buying something narrower than it looks, and it's worth knowing that before term starts rather than in September.
None of this is an argument against part-time or younger tutors as a category. Plenty are excellent, and plenty of full-time veterans have gone stale. But "experienced" has been drained of meaning by overuse. The more useful question is structural: is this someone's actual profession, done at volume, day after day, with real accountability for how it goes? Or is it a good side activity for someone talented who's mostly doing something else?
At Higher Nucleus, where I teach, this is a deliberate policy rather than a happy accident: every tutor teaches full-time, and the centre has chosen not to take on undergraduate tutors at all, on the reasoning that teaching well requires the kind of full attention a side job can't give it. It's a stricter standard than most places set themselves, and the fuller reasoning is written out on the page where we've explained it.
Worth asking, whatever tutor or centre you're actually sizing up: not how long they've known the subject, but how much of their working life is genuinely spent teaching it.