Sitting Square in Your Chair
The way you sit is important. To sit square in your chair, put your behind in the center of the seat. Your legs should bend at the knees and rest on the floor. Most kids are too short to do this, so use a footrest or find a box or a stack of books to place under your feet.
Sit so your back touches the seat back the whole time. Try not to slouch or lean over the keyboard while you type. A chair that has lower-back support can help you do this.