How can I show congratulations?

I just found out that my science teacher is going to be a daddy!
What can I do to show him that I am really glad for him, but isnt too over the top?

How about a nice card from the class? Fold a piece of posterboard in half to make a giant card that everyone can sign and draw something baby related on the front.

just make him a card and get a lot of people to sign it so you dont like stand out by being the only one to give him congrats.