Are the curling toes causing difficulties when he walks? Is he in pain?
Our son, too, wears arch-support orthotics (one flat foot, one with a high arch). He complained of foot pain (when he was 10) and the orthotics have helped with it. They are custom-made (happily, our insurance covers them 100%. But, if not, we'd pay $500, out-of-pocket). We also homeschool. But, really dislikes wearing shoes in the house and goes barefoot indoors. So, he only uses his orthotics in his outdoor shoes. He says his feet feel fine the rest of the time, so this works for him.
He inherited his feet from us (I have incredibly flat feet, dh has incredibly high arches). My feet have always given me problems (I had severe bunions as a child and had to have multiple surgeries for them when I was 14, lasting over 6 months). I have had multiple surgeries for Morton's neuromas, as well, as an adult. My feet are very sad!
I have had custom-made orthotics and they have always been very uncomfortable for me (and didn't change a damn thing). So, I stopped wearing the custom and switched to an OTC brand available at better shoes stores. These have been much more comfortable and are inexpensive enough, at $35, to change every 6 months. Voila, no more foot pain.
Several podiatrists (and, two orthopedists) told us that orthotics won't change the way a foot develops. It will do what it will do, orthotics or not. Orthotics will help support the arch and are needed if there is foot pain due to lack of arch support. But, orthotics will NOT change the foot, they only offer support.
I have a few friends that also have flat feet and have no problems whatsoever. They don't wear orthotics or better quality shoes (I'm jealous that they can get away with wearing strappy little sandals and I must wear my chunky Chacos!).
Many children have flat feet and they only become a "problem" when a doctor steps into the picture and speaks up! Here are some things to look for:
Does your child's arch re-form when he bears weight and stands on his toes? Does the arch appear when the foot is dangled in the air, as the seat of a chair? Is he complaining about pain? Does your child walk normally (lifts feet up when walking, not dragging; ankles straight, not bowing inward or out; has normal feeling, no sensory issues)?
For curling toes, he may only need something simple to keep his toes in-place, not arch support orthotics. Does he complain about his feet?
Honestly, unless your child has special needs (walking difficulties that have nothing to do with flat feet), is very overweight or is complaining of severe foot pain from routine activities, I'd skip any orthotics until they were much older. Make sure he has comfortable shoes with toe wiggle room and check them, frequently, for growth wear-&-tear. Give him foot massages in the evening (I've yet to meet a child that doesn't like them!). Listen to your child!