I love that article. Marcus du Sautoy, presenter of a number of good popular TV programmes on mathematics, says much the same. He once observed that we don't insist that young people have a complete and thorough grasp of spelling and grammar before we expose them to Shakespeare, whereas they are rarely allowed a glimpse of interesting mathematical problems until they've demonstrated a complete mastery of arithmetic.
During my daughter's brief time at school, her teacher wouldn't allow her to tackle the Primary Mathematics Challenge, insisting that she wouldn't do well and it would be discouraging for her, though dd was really keen. This prediction was based on dd's inability to remember all her multiplication tables. Luckily, the following year she had the chance to take the challenge through a home ed group and did really well. This was the group, if anyone is interested: groups.yahoo.com/group/PMC-Home-Ed/ but I'm not sure whether the same kind home-ed parent is still coordinating it. You can download the past PMC papers from the Mathematical Association if your child likes that sort of thing.