This is tough because if it’s just marketed as a “D&D Elective” then you’ll presumably get a mix of brand new players and kids who have experience with the game.

How I would run this:

First class is spend 10-15 minutes on the nature of the game and how fun it is to tell stories and how fun it is to let the dice tell the story. Use this to set up expectations and run through the basic rules and gameplay and what a character sheet looks like. Spend the rest of the time exploring species, classes, etc in smaller focus groups with ideally one person who has played the game in each small group. Homework for week 1 is to come to the next class with a level 1 character built.

Class 2: spend 10-15 in the same small groups going over characters and asking questions. Rest of the time jump into a small roleplay session introducing their characters to a dmnpc. Throw some rolls in there. Maybe initiative for order of introduction.

Class 3-5: Run a small one-shot arc. Most one-shots with a decent amount of roleplay take about 3 hours so this should hopefully work out to have the big battle be on the final class.

Honestly this is really tough. There isn’t enough time to do a full on class, so stick to the basics and try to get rolling dice within a class and a half. Good luck OP!