You didn't ask my opinion, but I'm going to share it anyway. As a teacher it would make me very uncomfortable being given a shower by my students. You have to be so careful about the "free public education" clause in the Constitution. If the parents are asked to contribute money or gifts, it's just not right.
As a parent, these sorts of things infuriate me! Showers are for peers, not people who have authority over you. I've given gifts the couple of times my kids have come home with the notes, but nothing of any value. For instance, one time we took pages out of an old ABC book we got at a garage sale and put three of them in Dollar Tree picture frames.
I don't have any problem with a celebration. When a coworker was expecting I had my class make a "Handy Tips for New Moms" book. They wrote their tips on index cards. I put the cards in a .99 photo book and we presented it to the teacher. She got a kick out of it and it didn't cost the parents or the students anything.