The challenge in TARC is to lift a given payload, with a given motor, to a predetermined altitude, and land within a predetermined flight duration. The variables are overcome using the rocket design (weight, drag), winds, air density, recovery system (parachute size), coast delay duration etc.
Our kids are practicing here at around 6000' msl, and the competitions are held near sea level in Washington DC...still another challenge. It's really satisfying to see them at work...