First barbell session for teens

I'm a teenager new to lifting and this is my first time with a barbell. Build me a 40-minute technique-first session that prioritises correct movement over load. Start with an 8-minute warm-up: 3 minutes easy cardio (jog in place, jumping jacks or skipping), then leg swings, arm circles, bodyweight squats x10, and hip hinges x10. Then teach me three lifts with an empty or very light barbell (just the bar, ~15-20kg, or a broomstick if the bar feels heavy): (1) back squat, (2) Romanian deadlift / hip hinge, (3) overhead or push press. For each: 3 sets of 5-8 reps at a very easy load where I could do at least 4-5 more reps (roughly RPE 5-6, so technique never breaks down), 90 seconds rest between sets. Give me 2-3 specific coaching cues per lift (e.g. where to look, brace, bar path), tell me what a good rep looks like vs a common mistake, and add one easy accessory like a plank (3 x 20s). Tell me when it's safe to start adding small amounts of weight. Keep loads light and form strict the whole way.