Honestly, you can make up the rules and incorporate as many or as few traditional D&D rules as you like.
But rule #1 is: Have fun! If a rule being used is bogging down gameplay or is boring, scrap it. Who cares.
STEP 1: Describe the scene. Five senses, 5Ws+H, etc.
STEP 2: Players can chat about what their characters feel, think, say, or might wish to do.
STEP 3: Roll a 20-sided die (d20) to determine unknown outcomes (any character can cross the street, but climbing a frozen waterfall could prove more challenging). The Dungeon Master (DM) determines how difficult an action is on a scale from 1 to 20 (or beyond). The higher the number, the more difficult it is. The same dice is used to determine how succesful an attack is. If the score is equal to or greater than a creature's Armour Class (AC), they land a hit.
If players are attacking, roll a damage dice assigned at character creation. In reality, a simple 6-sided dice (d6) will get the job done just as well. The higher the number, the more damage done. Add extra dice for extra damage if you're feeling spicy.
ALTERNATIVES: Really want to shake things up and ditch the dice altogether? Have players and the DM play "Quick Draw" (that game you see your students play where they double tap their legs, then cross their arms to block, or point their thumbs behind their heads to load, or point their fingers at their opponent to shoot) and give the DM extra "lives" as the monsters to increase the difficulty. It's hilarious and stressful.
I found the following documents and posters to be instructive.
How to be a DM (A brief guide with some YouTube videos)
D&D Beyond Free Rules (2024) (This is NOT light reading)
Go play or at least read through Peril in Pinebrook (it's very short).
One round of this, and the rest made so much more sense for me and my students.
Rules-lite, premade characters, and it provides a script on what to say and do.
Six Abilities Poster to print and hang in your classroom
Difficulties Class Examples Poster to print and hang in your classroom
Glossary of common terms in D&D
D&D Quick Reference poster
Basic Actions for Players (good one-pager to print for players)
Dungeon Masters Guild for an endless supply of affordable and often free adventures.
Running a D&D Adventure YouTube guide