Three years on from the tragedy, Hagley's headteacher, Paul Hill, believes that in marking the anniversary he must attempt to achieve a balance between compassionate remembrance and the turning of a page. "A school is a dynamic community, and the reality is that we have to move forward," he says.
At the mass, the theme of prayers and readings was "to celebrate that the children were with us, and that we are never going to forget them". The school itself has many physical memorials. "So many pointers and reminders," says Paul Hill. "The stained glass window, the memorial garden, the photographic display." By next spring Hagley will also have a new music block, partly paid for by public donations made in the aftermath of the tragedy.
Andrew Murray, a Hagley governor whose 13-year-old daughter Katie was killed in the accident, is well aware of the school's need to move on. "There comes a point where it doesn't mean the same. New children come, teachers change. It's all part of living," he says.
At the same time, it is clear that after any bereavement - whether communal or private - there will be people who cannot move on until they have begun to accept what has happened, and that this can take a long time.For them, too quick an attempt to return to normality may be inappropriate and distressing.
Steve and Liz Fitzgerald, for example, who lost their daughter Claire, aged 13, that November night, help to run the Bishops Wood Group, which gives the bereaved Hagley families and friends the chance to meet in a tranquil country setting. On the premises of a nearby nature reserve, they talk - if they want to - and express their feelings through art, drama, music and writing. Their own collection of writing, for which they are seeking a publisher, reveals how grief runs deep and long. "Even if I stay in your lesson," one pupil wrote, "I will learn nothing because my mind is constantly occupied with problems that I cannot deal with."
Multiple tragedies are thankfully rare, but death is not. Hagley itself has lost another pupil this year through a terminal wasting illness. Even more common is the child who has suffered loss, be it of a parent, sibling,friend, grandparent, or beloved pet, who brings to school a hurt that cries out to be acknowledged and respected.
And yet there is a feeling that many schools do not handle childhood grief and bereavement well. Schools are part of society after all, and for today's society death is "the last taboo".
Professor Oliver Leaman, of John Moores University, who studied the way that Merseyside schools dealt with the Hillsborough football ground tragedy of 1989, suggests that, "If you're a teacher, part of it is being very focused on the future, which makes death very worrying. And of course teachers are middle class, and middle class people don't talk about death very much." (He found that some Merseyside schools with affected pupils "completely ignored" the Hillsborough disaster.)
But teachers, explains Professor Leaman, are in the front line when children are in distress. "For a lot of children, school is therapeutic; they have good relationships with their teachers, who can be effective in helping them. If teachers do not respond, then children begin to wonder whether their own feelings are appropriate. There isn't a right or wrong way to grieve. There is the way that is appropriate to the particular child. "
Grace Jordan, of the Dove Centre, which offers bereavement care in North Staffordshire, emphasises the unevenness of children's reactions to death. "If you drew a graph of someone's grief, that of a child would have many more peaks and troughs than you'd find in an adult. It shows in behaviour. A child can be very distressed and then kicking a football the next moment."
Children who are not dealt with sensitively can stifle their feelings, because, for example, they want to spare the feelings of others. "An awful lot of children protect their parents," says Grace Jordan. "They say, 'Mummy's been crying enough and I don't want her to be more upset'."
Next week the National Society for the Prevention of Cruelty to Children publishes the results of an initiative called "Talking Blues", which found that loss and separation are major causes of anxiety and stress in children's lives. When a child's world has fallen apart, schools, with their sense of familiarity and security, can make a big difference, often in uncomplicated but kind and thoughtful ways. As the report says: "Quiet sympathy and basic normality is what most children in this situation want."