I assume you would have to homeschool (or unschool) until the child is 18 to avoid having to deal with government interference. However, given that there are no predetermined hours or times that you must tutor your child at home, and that you do not need to conform to the National Curriculum or undertake examinations or SATs, I wonder how the government could effectively check.
Other oddities are that if your child is expelled from school, he or she is not allowed during school hours to be in public places, unless you decide to immediately homeschool. And those parents wishing to take their child out of school for a three-month holiday should just write a letter saying they are homeschooling their child and then return their child to school when they are back from holiday.
I have no idea what the rules are governing children who pass their A-levels by age 10. Are they then allowed to play on their Xbox for the next eight years without further schooling? Again, I see no way that the government could check anyway.