Members of the school community, as well as friends and family, have paid tribute to the man who is said to have loved the outdoors.
Mourners were earlier asked to arrive dressed not to mourn, but to celebrate.
"Leslie would have liked a party, not a funeral,'' a family notice said.
Originally from Canada, he is the son of Peter and Judith Gelberger and brother to Eva.
He is also survived by wife Laura Gelberger.
His funeral comes as almost $45,000 has been donated by members of the public to the family he has left behind.
Gelberger was the sole breadwinner for the family and donations will go towards helping his wife and young boys.
To donate to the family, visit: Help for Laura and kids