tamarind: I think in general girls develop much faster than boys, though there are exceptions. I know girls who can focus for long periods of time since 3 years old, but it is rare to find boys like that. I strongly believe that boys who have short attention span can be trained to focus much longer. In the case of my boy, giving him one to one attention at home works wonders. But other kids may be different, it depends on many factors like the home environment, parents' expectations, the boy's personality, etc.
BTW, I am a full time working mommy, and I only spend about 30 minutes a day teaching my boy, but I can make him focus and that is more than enough for a child below the age of 6.
Yup. One thing for sure - no full-day child care or any amount of enrichment classes can replace the quality time that the parents spend with the children. We also try to spend at least 30 mins time with our boy everyday, to read story and do activities. Sometimes, he is also eager to show what he learn in school e.g. he will write the chinese character when he learn a new one and we encourages him, so it serve as a form of learning reinforcement. If a parent just send their kids enrichment programmes but does not participate in the learning process, then it will still not be effective.