Xinglu
Black Belt
They are segregated because they are run by seperate organizations.
There is an Explorer Scouts programs that is a subsidary of BSA that is coed and open to ages 14-20 IIRC. Explorers were usually associated with a profession (LE, fire, search and rescue, etc) but there were also High Adventure groups.
the BSA has the Venture Scouting which is Co-ed and from 14 - 21, they also have Varsity Scouting which is 14-17 (up to 18th b-day) and is not co-ed. Those would be your high adventure groups.