PhysicsTeacher,
Im a Technology Teacher and run a club in NY. Foosballclubsusa is a good site and John O'Brien (founder) was a Tech Teacher in NY as well, he is recently retired but is a great resource for this exact topic.
I have high school kids so they are first introduced to it in 9th grade. For brand new players I work on defensive strategies such as: keeping 2 men in the box, covering 2 different holes, moving them together as a unit, not panicking and getting squirrely, trapping the ball in defense zone, hitting the ball hard, hitting the ball at an angle.
For offence I work on getting possession, setting up shots, basic pull kicks, pull shots, push shots. Anything on the 5 bar (passing) comes a little later - most kids are right handed and very awkward with 5 bar and tend to just attempt 5 bar shots.
I only start with a few basic rules - no spinning, ready protocol, three touch serve, dead ball, jarring. I work more rules in as kids get better, passing moving ball, distractions, time limits, etc
I use kickertool.com to set up tournaments and keep stats on wins/losses/points for/points against to rank the players. I set up elimination/ double elimination/ round robin DYP with A players and B players based on their current rankings. I have two tables and usually get between 20-30 kids at our Tuesday Foosday tournamnets.
Good luck