We need to be realistic, we can't have everything. We want youngsters to continue their education and the risk to them individually is small. However there's an uproar when it is suggested that people from a population where the virus is relatively prevalent shouldn't be able to travel the length and breadth of the country, seeding the virus into more vulnerable populations. We can't have both.
For many families students will plan to come home for christmas, and within a short time afterwards will be mixing with relatives of all ages, often including the elderly.
They either need to stay at home where the risk of contracting the virus is lower, or go off to be inadequate relatively infectious bubble, socialise within their own low risk populations, but not come home at will, and certainly not at Christmas when so much intergenerational mixing is expected.
If students come home for christmas how can they not mix with elderly relatives, unless elderly relatives won't be invited for Christmas this year? In our family Christmas is a time when several older family members spend the day with us, when otherwise they would be at home on their own. It's also a day when social distancing is near impossible for many - spare chairs come out to accommodate everyone, more people round the table than normal, etc.
In my view students who don't want to go away and stay away should be supported to learn remotely, at home. Those who want to go off and have the student experience, c/w parties etc, should be able to do so, but on the proviso that they aren't coming back for Christmas. We wouldn't be talking about a few lonely people left behind when everyone heads home, their friends and room mates would all still be there. Many gap year students go off backpacking, missing a Christmas at home.