Santa or no Santa?

Someone at school told him there's no Santa that your parents buy everything that's why it's at the store and it all has labels and tags

He question everything and is sad I saw he went from happy excited to sad and it hurt my heart he seems so disappointed and disinterested in Christmas and angry that it's a lie.

I don't know what to do he's six and is getting older I'm not sure how to do Christmas? I'm not sure what to do gifts presents and Santa

What do you say to your children about Santa Claus?

Also What do you do if they didn't get what they imagined for Christmas and are upset?