Teaching improv to non-improvisers suggestions

Hi all,
I'm a school teacher and former improviser. My school has asked me to lead an improv workshop for the teachers and I would love to as I use my improv skills constantly throughout the day and think it's a super valuable skill as a teacher. Here's the rub, it's been a solid 3-4 years since I've done any improv and I've never taught a class. Does anyone have any suggestions of games/warm-up activities I can do or any helpful hints?

Things to note:
*I'll have about an hour and there will be probably 5-10 people there (I'm leading 1 of 4-5 groups)
*This is a one-time thing, I'm not looking to convert my co-workers into full blown improvisers, I just want to give them some tools and skills they can use and teach them these skills through games (like 3 line scenes)