Some experts state that skiing can be learned as soon as a child walks. This is quite true although the progression will be slower for very young children than for teenagers or young adults, because sports movements are learned by reference to other movements learned in other sports or activities (this is called "transfer of learning"). The younger the child, and the less motor skills references her or his brain has – and the more work his or her brain and body will have to acquire skiing-related motor skills from scratch.
This is no reason to stop though – the best skiers almost all started very young!
Sometimes around 3 years old is a great starting point depending on the child acquired motor skills.
For example, if your child can do what is shown on the
movie to the left, the learning curve will already be faster – as
you can see the 3-year old in the movie has acquired leg independence,
a good bit of coordination, and can shift accurately his weight from
one leg to the other – those are all skills that transfer really
well into skiing.
Depending on the sports the child plays and his or her motor skills, a good instructor
will vary approaches, and select exercises, or even a teaching method, appropriate
to the child motor-skill background.
On the right is a movie of another 3-year old, about
1.5 hours into what I am sure will be a promising, fun, and fulfilling