When Harry and his friends get left out of their teacher's wedding, they invite themselves!
The long-awaited day is finally here: Miss Mackle is getting married! The only problem is that she didn't invite any of her Room 3B students to the wedding. The kids don't understand it: a wedding is a time for families to be together, and they are Miss Mackle's Room 3B family—which is important since her father is in the military overseas and won't be home for the wedding. So Harry comes up with a plan to sneak his pals into the wedding ceremony. It seems like the kids are going to make a horrible mess of their teacher's wedding... until Major Mackle shows up just in time!