Examples of scaling could be using less weight, performing less repetitions or rounds than are called for, or doing an easier exercise (pushups instead of handstand pushups). Scaling is necessary to prevent injury and maintain progress. If performing a workout as prescribed will tax you to the point where you won't be able to do anything for three days - scale!
Kids absolutely need to scale! TennisWOD can easily be adapted for children/teenagers of any age. Will a 10 year old deadlift 225lbs (well, that would be really impressive but probably not). Can a fit 10 year old who weighs 100lbs be expected to deadlift between 50-80lbs? Yes. Good coaches at proper facilities will have all the equipment necessary to make these workouts accessible to any ability level.
