When it comes to materials used to make kids golf clubs, there are four things to look for:
Since children are not as strong as adults, they need lighter shafts. Steel shafts are too heavy for children; the last thing you want is for your child to struggle to swing the the clubs. Graphite shafts are both lightweight and inexpensive. Make sure the shafts are actually junior golf shafts and not adult shafts sawed down. Altering an adult golf shaft will change the flex and kickpoints.
Stainless steel irons are better than zinc or aluminum alloy irons because steel is a lot more durable. We recommend stainless steel irons for kids due to their durability.
Full titanium driver heads are durable and light-weight and come with a hefty price tag. You may have noticed that most advanced adult drivers will be made out of titanium. Some kids golf manufacturers sell titanium kids golf drivers, but are they really necessary? Generally speaking, titanium is unnecessary for a junior golfer unless he or she is very advanced. A junior golfer will fare just as well with non-titanium drivers for a fraction of the cost. Ti-alloy or aluminum alloy drivers are recommended for kids.
Ok, a manufacturer's warranty isn't a material, but it is something to look for when trying to pick a set of clubs for your kid. Even if you pick a set of clubs with the best materials, if they are built poorly, they will fall apart regardless of what they're made of. All manufacturers need to make a profit, and if they are willing to back up the quality of their products with a warranty, that probably means they're making a quality product. Some kids golf sets come with no warranty at all, and the best warranty in the industry is the Paragon's Rising Star which comes with a 1-year warranty on the entire club and a lifetime warranty against shaft breakage! Most other warranties are inbetween.