The opening paragraph of the article tells you that it was NOT, in any way, shape, or form, an honest mistake.
Not only was the picture removed... the names of the students were removed, as well.
I'm sure composition is all electronic these days, not how it was done in the dinosaur days when I was around, but I suspect that the text and photo were in different files, so their removal from the composition was a deliberate act because it would have taken multiple steps.