I already set that out, a child in care under s20 might be also subject to an ISO or SO, its unusual, but you cant tell without knowing the care status of the child.
For example, lets say a child is not safe in their parents care, the LA apply for care proceedings and an ICO but the judge does not grant this so child stays in mothers care under an ISO, while proceedings continue.
That can go in a number of directions, further down the line, more concerns might mean that the child is less and less safe but threshold for separation is not met (or judge and Guardian dont want separation). So mum agrees for s20 accommodation of the child but within a P+C placement. So now mum and child move into a foster placement for the CHILD, but the purpose of a P+C is that the child is cared for by the parent.
Or, using the same example, parent and child live at home, subject to proceedings and subject to ISO. Mum does well and parenting assessment is positive, proceedings come to the end and recommendation is that child stays in parents care and ISO is discharged and SO is made. Lets say its a 6month SO.
One day, there are significant concerns raised, perhaps child is police protected, perhaps SW visits and finds mum unsafe around the child. LA apply back to court as they can under the SO and agreement by parties is that mum gives S20 consent for a P+C and mum and child move into that so child is in care.
There are other combinations of circumstances leading to a child being both subject to an ISO or SO and also being a child in care without an ICO, but those are the ones that come to mind
A SO or ISO does not in itself indicate whether a child is in care or not.