Foster children are not a protected class under the law.
Perhaps foster kids could or even should be a protected class, however unlike most protected classes that have faced historical systematic discrimination codified in law, the general hardships of foster children are not based in unjust laws.
I have worked in Dependency law (ie with children that have been abused, abandoned and neglected) which deals a lot with foster kids.
I favor programs that provide funding for foster kids like this and provide assistance when they “age out” of care, but it is a broad brushstroke and doesn’t take into consideration individual situations as you suggest. In other words foster children are not all alike nor are their situations. Some live in group homes and they are just a number or a check for foster parents, some live in loving and supportive homes, even sometimes in the homes of relatives when parental rights were lost but they are still considered foster children. Some become foster kids at 17 and others are born into it. There is everything in between.
It is about the equivalent in terms of diversity of situations as being a minority/protected class that has historically been discriminated against.
Squint and we might start looking like college tuitions in Europe.
Seems like the opposite of universally accessible higher education regardless of background.