A.M.
http://www.aap.org/family/Carseatguide.htm
Age Type of Seat General Guideline
Infants Infant seats and rear-facing convertible seats All infants should always ride rear-facing until they are at least 1 year of age and weigh at least 20 pounds.
Toddlers/Preschoolers Convertible seats It is best to ride rear-facing as long as possible. Children 1 year of age and at least 20 pounds can ride forward-facing.
School-aged children Booster seats Booster seats are for older children who have outgrown their forward-facing car safety seats. Children should stay in a booster seat until adult belts fit correctly (usually when a child reaches about 4' 9" in height and is between 8 and 12 years of age).
Older children Seat belts Children who have outgrown their booster seats should ride in a lap and shoulder belt in the back seat until 13 years of age.