Children are born with flat chubby feet, this is part of normal development. As your child gets older there are many changes to their feet and lower limbs. At approximately 6 years of age, whilst still changing, you would expect to see an arch in their foot.
A more important indicator than the appearance of your child’s foot is function. Do they trip more regularly than children their age? Look for bruised and battered knees, pay attention when visiting children their own age. Do they complain of pain?