As your son becomes a teenager, you will find that he will go through many changes. All of the sudden, the toys and games that he loved when he was a little boy will not be as interesting to him anymore, and the different boy furniture that he used to play on and sleep on will no longer be big enough for him.
As a matter of fact, you will find that the kid furniture that you bought for him when he was four, or even eight years old seems like it is tiny toy furniture under his seemingly ever growing frame. This can be a very awkward time for your son, especially if he is going through many physical changes all at once. Because you want your son to feel as comfortable as possible, you may want to invest in young adult furniture for him so that he will be able to feel like he once again fits in. You may think that just a twin sized bed and mattress will be enough for your son, but the fact of the matter is, that unless you invest in one of the young adult beds that is made for taller people, and features an extra long mattress, your purchase may not be a comfortable fit for your son.
Take into consideration the fact that your son will be stretching both in height and width for the next few years, and try to find some type of young adult bedroom furniture that will be able to fit him comfortably for the next few years. Young adult furniture is made with the thought that your teen will be growing and be changing in shape, so it is more sturdy than most kid's furniture that can be found.