If he's away at uni and won't be driving much, it makes sense to think carefully before paying for a full year.
Temporary (short term) cover does exist, but for a newly qualified driver it's usually priced per day or per week at a rate that works out far more expensive than a normal annual policy, so it only makes sense for a few days here and there, like driving home at the end of term. If he'd be using a car for a few weeks over the summer, it's worth getting a couple of quotes to compare, but don't assume it will be the cheaper option.
A few things that might help depending on what you're actually trying to do:
If he's borrowing your car occasionally, ask your insurer about adding him as a named driver, or about a "driving other cars" extension. Be wary of this one, as it's rarely offered to new drivers and often excludes anyone under 25 or with under a year's experience. Check the small print before relying on it.
If it's his own car sitting at home most of the term, look at whether you can keep it insured at a lower cost with a reduced mileage limit, or whether the insurer will let you pause it while it's kept off the road (SORN only applies to the vehicle tax side, so you need to sort the insurance separately). Some insurers will drop cover to "storage" level, which is much cheaper, but it means he can't drive it at all in that period.
A black box policy can also work well for a student who won't drive much, because the price reflects how much and when he actually drives, though check for restrictions on night driving and mileage caps.
Whatever you go for, get quotes from a few places, including smaller specialist new driver insurers rather than just going through a comparison site's top three. The cheapest price often comes from a provider that doesn't show up first.