At the moment, the parent is seriously ill. Bear in mind he or she may have died by next term. But whether the situation stays the same or becomes a bereavement issue, teachers can take steps to improve behaviour and remain supportive.
Firstly, it is important to recognise that erratic behaviour is entirely normal in these abnormal circumstances. Pupils may be saving all their best behaviour for home. At school, it could be time to let off steam.
"Anxiety and worry often comes out as anger," says Jenny Frank from the Children's Society. "They may think, `Why me?' At home they're responsible, but at school they may just snap."
This can go one of two ways: either they lash out, exhibiting rude, grumpy, surly or insolent behaviour; or they become quiet and withdrawn, which are easy qualities to miss in the clamour for attention.
The temptation is to turn a blind eye to misbehaviour. In fact, affected pupils will be crying out for boundaries and a sense of continuity. Adopt a "normality with compassion" approach, advises Jill Adams, schools training and support co-ordinator at the Child Bereavement Charity.
"Expect normal standards of behaviour," she says. "There will be times when it is appropriate to be flexible, but children tell us that the last thing they want is to be treated differently at school."
Acknowledge that their behaviour has slipped, but also that things must be tough for them right now. Children crave this sort of recognition and understanding. Point them towards a school counsellor or mentor - just a 20-minute chat each week will give them the headspace they need to concentrate in class.
"Some teachers avoid talking to a pupil about a sick parent in case they inadvertently upset them," says Catriona Matthews from Winston's Wish, a charity for bereaved children. "But if they are given the opportunity to let it all out through talking, it is less likely to spill out as bad behaviour."
On a practical level, review pupils' workload. With a sick parent to attend to, homework or coursework may not be the number one priority. But if they are under pressure to complete work, it can lead to stress-induced outbursts.
"Look at their timetable," suggests Ms Frank. "What is urgent and what deadlines could be extended? This will take some of the stress off the child."
Give them permission to call home from a quiet place at break or lunch; they may want to make sure everything is alright or that medication has been taken. Pupils will appreciate these small gestures. They may not want to talk things through, but they will be grateful that someone is thinking about their needs as well as their parent's.
These measures could be scuppered if the pupil is kept in the dark about their parent's illness. Ms Matthews believes children are still aware that something is not quite right, even if they haven't been told directly. "They pick up on the non-verbal clues, such as if a parent is absent a lot or displaying unusual mood swings," she says. "Things are different, even if they don't know why."
Children caught in this situation are more likely to look to themselves for answers. They may blame themselves for the changes or feel a sense of guilt or shame.
Teachers have to tread carefully here. On the one hand they must respect the parent's wishes, but on the other they must give pupils the space they need to talk about things that are on their mind.
A simple: "I've noticed you're not yourself at the moment. How are you feeling?" will help, says Ms Matthews. It indicates that you are there for them should they want to get things off their chest.
If detentions are still required, try to impose them at lunchtimes. Pupils may need to rush home or pick younger siblings up after school.
If the parent does die, say something. Usually, just how sorry you are. A wall of silence will not help pupils come to terms with such a life- shattering loss
Tackling this pupil behaviour problem