Hi, first it's good to know they are different from each other
the importance is in knowing how each has it's own part to play in identifying the accomplishments of a child, what milestones have been reached and when, they enable charting of a child or young person's development to happen and provide a structure or picture that can measure where a child might be in need of support or extension.
Rate/Speed involves a time frame linked to age.
Sequence/Order involves patterns and an order of development linked to body, mobility and intellectual growth - sequence can include an order that's both positive and negative - deterioration.
Rate - what happens at 1 year old, 24 months old, 7 years old ..
Sequence - how things happen in an expected order, sequence ie: breastfed, weaned, full meals. lie, sit, crawl - maybe, stand, walk, run..
Sequence, rate or age at which an individual reaches different stages of development will differ/vary - it could be that one child loses their first tooth at 5 years old and another child when they are 8 - expected development would be that a first tooth comes away at 6/7 -
BDHF the sequence of tooth loss is milk/first teeth appear, are lost, adult teeth emerge.
birth to five development timeline on NHS parental guide.
CYP 3.1 - unit 022 or - unit 1 Child and young person development
022 or CYP 3.1 CYPW PDF unit
Download all unit pdfs in zipped files at the foot of this
archived CWDC page
Development thread - links and resources
Level three handbook search on amazon & child development guide - Carolyn Meggitt
Hope this helps a little more