If your child is tired all the time, it could mean that they're not getting enough sleep. It could also mean that maybe there's too much activity for them during the day or maybe they're not getting restful sleep. So it might appear that they're sleeping but perhaps they're really awake or not getting a deep enough sleep.
Typically, 2-year old and 3-year olds still nap during the day. You know, by 5-years old, they're not really taking a nap anymore and we all know that a lot of children tend to be over-scheduled. A lot of times you have play dates, you have classes, you have a long day of school, and then they have piano or gymnastics. That can be a lot. And what's important to know is that sleep and the nutrition kind of go hand-in-hand. So are they eating enough and are they eating the right kinds of foods in order to give them the amount of energy that they need to complete their daily tasks?
What's important is to observe them, to take note of when are they tired. Is it every day after school? Perhaps there's something going on in school. Is school too long of a day for them? Try to make adjustments and changes and see if that makes a difference. Maybe give them a break between school and the activity and perhaps they won't be so tired. And discuss with your pediatrician.