I had 7 years of braces (grades 5 through 11) when I was growing up. My jaws were too small and my teeth were too big (and I had a gap between my front upper 2 teeth I could put my thumb through). Besides pulling the wisdom teeth, they had to pull out 4 other adult teeth as well in order to get everything to fit.
I was so worried my sons teeth were going to be like mine instead of his Dad (his teeth are straight and he never had braces). The first panaramic xray the dentist did on his teeth looked like there was a traffic jam happening under his gums. So many teeth forming and little or no space in his jaws for them to grow out. So in the 2nd grade he started wearing an expander retainer. It was ok, and it was slow, but at least he only had to wear it at night (and he couldn't lose it at school). When we moved, we continued the retainer at night through third grade, then our new orthodontist had an expander that couldn't be removed put in his mouth toward the end of 4th grade. It only took 6 weeks of expanding (then 6 months of leaving it in place to hold the expansion open) and he was finished with that part. Then the real braces started. Right now he has 9 months of braces left until he is finished, and he'll be finished before he is out of 6th grade. And his teeth are beautiful!
Back when I had braces, they tended to do the work on kids when they were older. The palate is more developed then (the bones grow and knit at the roof of your mouth), and moving the teeth then is very very painful. If they can expand the jaws and palate before the bones knit - it hurts a lot less, and because the jaw is large enough for the teeth to fit, there is less moving them around. If you can get the teeth straightened out now, you spare your child a life time of fillings, root canals and dental troubles.