Unless you are an experienced skier we highly recommend you take lessons. It's most cost effective to take group lessons and they also give the benefit of being quite social and great fun. Plus they're not as "full on" as private lessons. If you're a beginner they're essential.
Private lessons as an individual, or a small group of friends/family, are a great way to improve quickly, or for a refresher if you haven't skied for a while.
Lessons also are a great way to learn to navigate around a new resort. They also allow you to make the most of your holiday if the visibility is poor.
Here are links to some of the more popular ski schools in Chatel
ESF Ski School (Ecole Ski France)
http://www.esf-chatel.com/en/courses.html
British Alpine Ski and Snowboard School (BASS)
Please note; this company only employs native English speaking instructors teaching in English
http://www.britishskischool.com/BASS_Resorts/Chatel
ESI (Ecole Ski International)
http://www.esichatel.com/?lang=en
More are available here:-