The story is about "my high school life".The student council had a fund raiser where we could buy a flower for someone special and have it delivered to them on Valentine's Day morning. Finally that moment came, and a delivery person entered the room carrying a massive bouquet of flowers for distribution thirty minutes after Mr.Aaron's math class had begun.I am not certain. It depends on what they were doing before this started, and how they usually treat Mr. Aaron. It could be that Mr. Aaron hadn't had their attention before, but that for some reason they were interested in what he would find in the cards, or do with them.
"Anticipation" suggests that they expected something exciting to happen.
Sometimes quoted sentences aren't sufficient context. It may be more useful for you to tell us something about the story.
Got it.But what about at long last?Does it mean at last? or for a long time here?I think it means that everyone quieted down by themselves, without being asked, because they were so interested in what Mr Aaron would do.
The fact that he finally had their full attention suggests to me that usually the students usually paid attention to other things during the class, rather than concentrating on what Mr Aaron was trying to teach them.