I also think a healthy plan of lots of physical activity is very helpful. anything that really works muscles is good---- climbing a play structure, doing the monkey bars, swinging, running, kicking a soccer ball, swimming (at an indoor pool when cold out), rolling down a hill and running back up, riding a bike or scooter, doing tumbling classes, etc. As much as this as you can fit into a day can have an overall calming and organizing effect on a child.
My son has sensory integration disorder---- I'm not suggesting your daughter has this from the tiny bit of info you give, but for his inability to sit still and focus, we do plenty of 'heavy work' which is the physical activity I've just mentioned to calm him down, get him regulated to focus, and help him sit.
also agree that good rest is critical as well. good luck
the first thing that you can do is to make sure that she gets a good nights sleep! Make sure she does not have sleep apnea! Ask her teachers if she seems much worse then the other chldren. She is 5? When is her birthday and what level of school is she in? How long is her school day?
She is only five. In time she will settle down, but she may always be a lively child. You mention no other problems, so there is no reason to be concerned. If you know someone with a big family, observe the children. You will see markedly different character and personality traits. Such diversity is normal and desirable. If you have only one child, this may distort your vision of what is normal and what is worrisome.