I teach at in an international program at a public elementary school. The headmaster wants me to teach either debate or public speaking to the 4th and 5th grade. I dismissed the idea of a debate class pretty much immediately and have decided to do a public speaking class. I am having trouble finding age appropriate resources. I have looked into the toast master youth program and found a 4H public speaking activity book but that's about it. The class has to last an entire semester, 16 one hour classes, give or take. In addition to units on the types of speeches, how to write the various parts of speeches, body language etc, I am thinking about having the kids do two short speeches each over the course of the semester. Honestly, I don't even know how I am going to get a room full of 4th graders to sit through 35 of their classmates speeches without going bananas.
Does anyone have any suggestions for materials or even how to structure the curriculum? Any help would be greatly appreciated.

Forget about public speaking and go for the debate. You can spend several classes going over the rules and such. Make them fun. I taught debate in Korea to one of my classes and they really got into the arguing part of it. We all had a blast and the other teachers and principal and VP came to watch too.

how I am going to get a room full of 4th graders to sit through 35 of their classmates speeches without going bananas.

Peer checking + video recs.

I divide my classes in 3-4 groups (or let them choose groups) and then I find emtpy classrooms for them to do their presentations with their groups and have their friends mark them with a rubric. There are many to be found online if you need one. Currently, because of COVID we are having them meet on Microsoft Teams and send in their presentations like that, which could totally work as well post-Covid.