I have had actually this experience the last couple of years with some Catholic children in religious education sesssions. Because we have been so politically correct that children no longer hear or see that Jesus was born in a manger and died on the cross, they may come to us, if their families have not been practicing their faith with absolutely no background. They simply have never heard the stories. Their only associations with Christmas and Easter may be from commercials on TV - Santa, the Easter bunny that clucks like a chicken, etc. - and from family celebrations of gift-giving on Christmas - and perhaps little or nothing (at most a big family dinner) at Easter - the most important celebration of the Christian year.
This is a call to evangelize our children - especially in a climate where parents tend only to insert them in religious formation to "get their sacraments". The sacraments of initiation have pretty much no meaning apart from the practice of our faith, including regular participation in the Mass and Eucharist. If not to be able to come to the Eucharistic table on a regular basis, what are kids being intitated for?
We need to tell the stories - loudly and often - of our faith, and of our God, so that the children can hear that God is alive and active in the world... and in their lives.