Hmm, I wish I have saved the article that discussed about introducing manga to school and positive benefits it can bring.
To me, I would rather have student at least read something than nothing at all. It's not about pictures, but how it was putted together.
Here's one link, maybe it will bring you a new perspective on how something like this can be beneficial.
Reading Online - New Literacies:
Remember, everyone's different. Some people might have benefited from this more than reading a regular book. Only if teachers are opened mind about this.