Better yet I would tell her/him what you liked about their class and how they taught it. To most teachers the job can get a little boring as they seem to be churning out a mill of students and grades. The occasional nice note is something that can make their day, but I would include details on why you liked it. Then they would have positive feedback on what they did right and can push that in the future. If nothing else it is a nice thought, most students want to go on Christmas break and forget school and their teachers as fast as possible. By showing a little extra care and attention you can make sure you are memorable to them and even make the year memorable to them.

At least it can’t hurt. Showing that you are a nice person and care about others is the true Christmas spirit and many people don’t remember this. If you show it then you are showing the spirit of the season.