If we don't want our children attending school, why would we want them graduating from one? If something is wrong with school, why do we want their stamp of approval?
What worked for us was to have the kids take the ACT when they decided they wanted to go to college. They scored very well (got fabulous scholarships) and were never asked for HS diplomas or GEDs. I guess if you can do the algebra, etc. on the ACT, they figure you "graduated."