So a kid drops his math triangles on the floor. I take them to the board and draw a small house shrine (or maybe it wasn't; I also drew a portrait of some man in a picture frame so I could have been drawing a funeral thing--we'll get to why it's bad that I don't really know) and some incense and a plate of mikans. Then I place the triangles there as if I am making an offering to my ancestors.
The kids thought it was hilarious.
When the teacher finally noticed, she thought it was sacrilegious. She sternly said, "We don't do that," and erased it. Then she turned to the class and said something quickly with the word "joke". I'm not sure if she was covering my actions or denouncing them.
So a couple of factors go into my surprise, and my やっぱり "I shoulda known" feelings about the matter.
Factors that made me think it was okay:
The Japanese aren't religious. They often seem pretty proud of how religious they aren't.
I was talking to the other teacher before class, and she joked about how if you don't honor your deceased grandma with a snack offering, she will turn into a vengeful ghost. So I had it in my head at the time that one can joke about that very thing.
There are many scenes in animes and comedies where I have seen people joking about funerals. Please see this video for what I am talking about with the funeral funnies.
The kids seemed to think it was funny.
Factors that should of let me know that things would suddenly take a turn for "I'm sorry I just insulted you and your entire culture":
The Japanese are religious, or at least ceremonial in a Confucian way. Even though many of them proclaim no religious beliefs, almost everyone still has those home shrines. All the festivals, save our Saga balloon festival, have religious overtones.
Funeral stuff is taboo. My students were shocked when we had a discussion in which I stated that sticking your chopsticks in your bowl and standing them that way is not rude. Shoulda foresaw that related stuff would be bad too.
That teacher takes everything I do seriously. For instance, I described a guy as a "the one that is a little chubby" when at a loss for a name, and she heard me across the room and was like, "What did you say?!"
A funeral is not the same as a home shrine. Once again, I am too culturally ignorant to know if I depicted a shrine as I intended, but in any case, I don't know some of the taboos going on, so while it may be okay for comedians on TV (afore-posted video link), there are rules to the comedy I might not get.
The children are aliens. No, seriously, any middle school teacher in Japan will tell you that. Ask them about the alien thing. What it boils down to is the children may have thought it was okay to laugh because they are not yet indoctrinated.
The Japanese are superstitious. Usually only in a "this will bring me good luck" way, but still.
So, yeah. Sorry bout that Japan.