Children adopted from foster care normally receive Medicaid to address various health needs inherent to growing up in abusive and neglectful environments. Most states consider them "special needs."
When a child turns 18, several states including Florida, remove these children from Medicaid Coverage, changing their medical and therapeutic services, regardless of whether they are still attending high school. Ironically, many of these same states require parents to continue paying child support and health insurance beyond age 18 if a child is still in high school.
Statistically, if these children were not adopted and aged out of foster care, they would likely be incarcerated and/or receiving benefits well beyond 18. An abused student's 18th birthday shouldn't take away health coverage