Catholics traditionally remember the dead during the month of November.

November Lists
The traditional practice of November Lists can work very well in schools. Each family is sent a blank list and invited to record the names of members of their family who have died. These lists are then collected and placed before the altar and Mass or prayers said each day during November.
Resources for November Lists

Bethany Mass
Some schools celebrate a Bethany Mass each year in November to which families who have suffered a bereavement in the past year are particularly and personally invited. The wider school community is also invited and many who have been personally invited in previous years come back each year.
Recources for the Bethany Mass

Remembrance Service
Many schools remember those who have died in war by marking Armistice Day on or near 11th November.
Resources for Armistice/Remembrance Day Service