That’s actually an interesting question and I guess there is no ultimate answer. Just because there really is no such thing as guitar strings that are specifically made for beginners.
However, when you look at all the different kind of strings that are available, there is no doubt in my mind that nylon strings are best suitable for beginners, especially young children. With that being said, it obviously all depends on the type of guitar you use. If your heart’s set on starting out with an electric guitar, then nylon strings will not work.
But as a guitar teacher, I would strongly recommend that you start with a classical guitar first. And just to be clear, because I sometimes get this question: using a classical guitar doesn’t necessarily mean that you have to play classical music. However, a classical acoustic guitar has the advantage that is comes with nylon strings. When you never played before, your fingers will hurt as you start practicing the instrument. And unfortunately, there is no way around that. This is true even when you use nylon strings. However, they definitely hurt less when compared to playing guitar that use steel strings, such as electric and western guitars.
Ideally, a new guitar student should use a nylon strings for the first three months. By then he will have developed enough strength in his fingers and playing hands that an ‘upgrade’ to a western or electrical guitar with steel strings is less problematic.
In sum, as mentioned in the beginning, nobody can ultimately say what the best guitar strings for beginners are. And there are even some guitar teachers who simply disagree with me and say that it really doesn’t matter whether you start out with nylon or steel strings. But I can only base it on my own experience as a player and teacher and I do believe that there is a difference. That’s why I for example recommend in my Beginners Guitar Course to use a classical guitar, if you have the choice. It’s just a little easier on your fingers.