Group Ski Lessons
Practically every ski or boarding school offers group lessons, where you sign up for a class aimed at people with a particular skill level - there are usually about six, from complete beginner ('never ever', as they put it in the States) to expert. In some resorts they run only in the mornings, or only in the afternoons, while in others you are expected to sign up for both.
For some people (especially in Europe), skiing and ski classes are synonymous. (The omission of boarding at this point is deliberate: snowboard classes are not nearly so popular.) Joining a ski class not only gets you tuition, but provides a group of companions who are, in theory, all of much the same level of competence. If you are going on holiday alone, or in a group that mainly doesn't match your standard, this may be very valuable.
Classes are of course much cheaper than hiring a private instructor. In Europe the cost ranges from the trivial in Bulgaria or Romania (roughly £55 for six days) to the not so trivial in big-name French and Swiss resorts (as much as £105 for six days). The cost is much higher and much less variable in the USA, although it must be said that the schools are on the whole better run there. Sample costs: Heavenly, California £90 for three days; Aspen, Colorado £100 for three days; Killington, Vermont £85 for three days. These high costs are one of the reasons why Americans are not in the habit of spending their whole holiday in ski school.
The downside is that in most classes you spend a lot of time standing around listening, watching or waiting (usually with mounting apprehension) until it's your turn to perform ineptly before your classmates. Not only is this boring (and sometimes cold), but it interferes with the important business of practising whatever skills you have.
The standard of tuition in classes is in general highly unpredictable. Some schools are better run than others, and build up better reputations. Where possible, Where to Ski and Snowboard resort descriptions include evaluations of the alternative schools in each resort. But in the end you are always in the hands of one individual instructor, who may or may not have the skills, inclination and patience to teach you effectively.
One thing that is always worth looking for in a school is a low class size. The big money-grabbing national ski schools in the Alps are quite cynical about class size. If they get the customers in high season, they will cheerfully operate classes with 15 or 18 pupils. You will find in many resorts now that the schools that aim to satisfy their customers (as opposed to fleecing them) will guarantee class sizes of no more than 9, 8 or even 6. Naturally, there is always a risk that schools like this will not have room for you unless you book ahead.
For more tips and advice on learning to ski: Teaching yourself to ski | Private Ski Lessons | Indoor ski slopes and dry slopes