As so often, we are mixing things up on here.
It seems we are talking about four different books, in total. There is "Diary of Young Girl: Anne Frank" which is the first published version I read in high school, on which was based a great play and a great movie. There is the original handwritten diary that Anne started soon after going into hiding. There is
Het Achterhuis (The Hiding Place) a second version Anne wrote in the latter year of her hiding, which she hoped would be published. In that version, she left out some of the sexual passages she had written at thirteen.
Likely Anne's father based the first published version on some combination of the original diary and the second draft Anne was working on when captured. How authentic that published version is, or how much embellishment was done, I have no opinion on and probably should be discussed on another thread.
There are two versions of Anne Frank's diary. They are called version A and version B. Read more about the differences between these versions.
www.annefrank.org
Then there is the comic book version, intended for the dumbed down audience that is the student body at a progressive run public school.
I don't see in that article exactly which version was being taught, nor what passages were read aloud. That would be the key to the story, yet those "journalists" chose not to tell us.
If that teacher took the opportunity to dwell on the sexual parts of any of those versions, rather than focusing on the larger lesson of the humanity of the Jews being treated like animals, then that was inappropriate and she was right to apologize.
It is not uncommon for pubescent boys to see pictures of nude victims of the holocaust being herded into "showers" and be more interested in the nipples and pubic hair than in the tragedy of the scene. That is understandable in children, but it is the job of educators to help them grow up, not join with them in order to spread the amazing news that as children become teenagers, they have sexual thoughts.