Before second birthday
Level I	Infants move in and out of sitting and floor sit with both hands free to manipulate objects.
		Infants crawl on hands and knees, pull to stand, and take steps holding onto furniture.
		Infants walk between 18 months and two years of age without the need for any assistive mobility device.
Level II	Infants maintain floor sitting but may need to use their hands for support to maintain balance.
		Infants creep on their stomachs or crawl on hands and knees. Infants may pull to stand and take steps holding onto furniture.
Level III	Infants maintain floor sitting when the low back is supported. Infants roll and creep forward on their stomachs.
Level IV	Infants have head control but trunk support is required for floor sitting. Infants can roll to supine and may roll to prone.
Level V	Physical impairments limit voluntary control of movement. Infants are unable to maintain antigravity head and trunk postures in prone and sitting. Infants require adult assistance to roll.
Between second and fourth birthdays
Level I	Children floor sit with both hands free to manipulate objects. Movements in and out of floor sitting and standing are performed without adult assistance. Children walk as the preferred method of mobility without the need for any assistive mobility device.
Level II	Children floor sit but may have difficulty with balance when both hands are free to manipulate objects. Movements in and out of sitting are performed without adult assistance. Children pull to stand on stable surface. Children crawl on hands and knees with a reciprocal pattern, cruise holding onto furniture, and walk using an assistive mobility device as preferred methods of mobility.
Level III	Children maintain floor sitting often by “W-sitting” (sitting between flexed and internally rotated hips and knees) and may require adult assistance to assume sitting. Children creep on the stomach or crawl on hands and knees (often without reciprocal leg movements) as their primary methods of self-mobility. Children may pull to stand on a stable surface and cruise short distances. Children may walk short distances indoors using an assistive mobility device and adult assistance for steering and turning.
Level IV	Children floor sit when placed but are unable to maintain alignment and balance without use of their hands for support. Children commonly require adaptive equipment for sitting and standing. Self-mobility for short distances (within a room) is achieved through rolling, creeping on the stomach, or crawling on hands and knees without reciprocal leg movement.
Level V	Physical impairments restrict voluntary control of movement and the ability to maintain antigravity head and trunk postures. All areas of motor function are limited. Functional limitations in sitting and standing are not fully compensated for through the use of adaptive equipment and assistive technology. Children at level V have no means of independent mobility and are transported. Some children achieve self-mobility using a power wheelchair with extensive adaptations.
Between fourth and sixth birthdays
Level I	Children get into and out of, and sit in, a chair without the need for hand support. Children move from the floor and from chair sitting to standing without the need for objects for support. Children walk indoors and outdoors and climb stairs. Emerging ability to run and jump.
Level II	Children sit in a chair with both hands free to manipulate objects. Children move from the floor to standing and from chair sitting to standing but often require a stable surface to push or pull up on with their arms. Children walk without the need for any assistive mobility device indoors and for short distances on level surfaces outdoors. Children climb stairs holding onto a railing but are unable to run or jump.
Level III	Children sit on a regular chair but may require pelvic or trunk support to maximize hand function. Children move in and out of chair sitting using a stable surface to push or pull up on with their arms. Children walk with an assistive mobility device on level surfaces and climb stairs with assistance from an adult. Children commonly are transported when traveling for long distances or outdoors on uneven terrain.
Level IV	Children sit on a chair but need adaptive seating for trunk control and to maximize hand function. Children move in and out of chair sitting with assistance from an adult or a stable surface to push or pull up on with their arms. At best, children may walk short distances with a walker and adult supervision but have difficulty turning and maintaining balance on uneven surfaces. Children are transported in the community. Children may achieve self- mobility using a power wheelchair.
Level V	Same as between second and fourth birthday.
Between sixth and twelfth birthdays
Level I	Children walk indoors and outdoors and climb stairs without limitations. Children perform gross motor skills including running and jumping but speed, balance, and coordination are reduced.
Level II	Children walk indoors and outdoors and climb stairs holding onto a railing, but they experience limitations walking on uneven surfaces and inclines, and walking in crowds or confined spaces. Children have at best only minimal ability to perform gross-motor skills such as running and jumping.
Level III	Children walk indoors and outdoors on a level surface with an assistive mobility device. Children may climb stairs holding onto railing. Depending on upper limb function, children propel a wheelchair manually or are transported when traveling for long distances or outdoors on uneven terrain.
Level IV	Children may maintain levels of function achieved before six years of age or rely more on wheeled mobility at home, school, and in the community. Children may achieve self-mobility using a power wheelchair.
Level V	Same as between second and fourth birthdays.
Distinctions between levels I and II
Compared with children in level I, children in level II have limitations in the ease of performing movement transitions, walking outdoors and in the community, the need for assistive mobility devices when beginning to walk, quality of movement, and the ability to perform gross-motor skills such as running and jumping.
Distinctions between levels II and III
Differences are seen in the degree of achievement of functional mobility. Children in level III need assistive mobility devices and often need orthoses to walk, whereas children in level II do not require assistive mobility devises after four years of age.
Distinctions between levels III and IV
Differences in sitting ability and mobility exist, even allowing for extensive use of assistive technology. Children in level III sit independently, have independent floor mobility, and walk with assistive mobility devices. Children in level IV function in sitting (usually supported), but independent mobility is very limited. Children in Level IV are more likely to be transported or to use power mobility.
Distinctions between levels IV and V
Children in level V lack independence even in basic antigravity postural control. Self-mobility is achieved only if the child can learn how to operate an electronically powered wheelchair.