Any of the following poems and readings are suitable, depending on the age and maturity of the students concerned:
‘Death is nothing at all’ by Canon Henry Scott Holland
http://www.skdesigns.com/internet/articles/prose/death.html
‘Do not stand at my grave and weep’ by Mary Elizabeth Frye
http://www.worldprayers.org/frameit.cgi?/archive/prayers/celebrations/do_not_stand_at_my_grave.html
‘What is dying?’ by Bishop Brent
http://www.poeticexpressions.co.uk/POEMS/What%20is%20dying%20-%20Bishop%20Brent.htm
‘Remember me when I am gone away’ by Christina Rossetti
http://www.bartleby.com/101/787.html
‘When I die If you need to weep’ by Merrit Malloy
http://www.inspirationpeak.com/endingsandbeginnings.html
Alternatively this reading from the Old Testament can have a calming, mantra-like effect, which will set a suitable tone to return to more mundane matters:
Ecclesiastes 3.1-8: A Time for Everything
There is a time for everything,
and a season for every activity under heaven:
a time to be born and a time to die,
a time to plant and a time to uproot,
a time to kill and a time to heal,
a time to tear down and a time to build,
a time to weep and a time to laugh,
a time to mourn and a time to dance,
a time to scatter stones and a time to gather them,
a time to embrace and a time to refrain,
a time to search and a time to give up,
a time to keep and a time to throw away,
a time to tear and a time to mend,
a time to be silent and a time to speak,
a time to love and a time to hate,
a time for war and a time for peace.