Can you suggest me some fun Christmas-themed game for 6-year-old children in a small classroom?

Pin the red nose on the reindeer.

Pass the parcel? Not traditionally Christmas-themed, but great for that age group and it features unwrapping presents. Kids sit in a circle, so space should not be an issue. Obviously, play Christmas music.

Here’s instructions: https://www.wikihow.com/Play-Pass-the-Parcel. I’m most familiar with the musical version, but the second kind – where there’s a small gift under every layer.

It might also be fun to do a scent challenge. Christmas is a very sensory holiday, in my opinion. You could use small bottles or boxes and cut a tiny hole in the top. Have some christmassy and aromatic items like cinnamon, cloves, mandarin orange, candlewax, needles from a fir tree, crushed gingerbread…the kids could learn to identify the different smells and match them to pictures of the items.

Lastly, if you don’t have many kids: decorating your own giant Christmas cookie or gingerbread house is always a hit. However, that could get very, very messy in a large group.

Musical Chairs was one that we played a lot when I was little. Back then we had a record player & the kids marched around the chairs until the music stopped (by the teacher) & the kids would sit. Of course, you’re one chair short of the number of kids playing & you remove one chair every round. You play until there is only one chair left. The last kid sitting gets a gift. You could play a Christmas song on your cell & when you hit pause & the song stops, the kids sit. You got to be careful to NOT hit pause when your favorite kid is in front of the chair or the kids might fire you. Other than that, it wasn’t a terrible game!!!

Red rover and duck duck goose.

There are simple Christmas crafts they could make. I made candy cane reindeer when I was a kid and I helped my sons class make them when he was in kindergarten.
http://onelittleproject.com/candy-cane-reindeer/

A great German Christmas tradition is this.
Bring in a Nikolaus with a bag of small presents.
He will give presents to the good kids, and for the bad kids, he lists some of the bad things they did that year, and threatens to spank them with a bunch of twigs. So they have to promise to be good next year, then they get their present.

Dreidel.

Look up Christmas Bingo on Amazon.

Thank you so much for answering. I am planning for a big party that will give the kids some good memory. Everything is still on the drawing board so every suggestion is welcome.