I have a personal bias about early childhood education. I strongly believe that the best place for a child in the early years is at home. Yes, I know some homes are horrendous places -- that's beyond the scope of this discussion. Given a reasonably healthy home environment, I think children should spend most of their first seven years or so with their families and friends and not in a structured setting that looks anything like our modern educational factories.
Unfortunately, keeping 'em home is infeasible for some families and undesirable for others, so a school option needs to be available. But in my ideal school, the learning environment for these young children is as close to a home atmosphere as possible. Very informal and unstructured. No grade levels--a multi-age group all learning together. One teacher for maybe 8-10 children at most. It would be awesome, in fact, if that teacher could have her classroom in her own home, like many daycare providers work out of their own homes. Call these first few years Primary School. Something like that. A more creative name would be good, but I'm not creative like that.
There are three primary goals for students at this age. The first is for the teacher to get an idea of each student's learning style. Are they more of an auditory learner, a visual learner, a kinesthetic learner? Are they more left-brained and systemic, or more right-brained and random? Do they need noise or quiet, activity or calm, etc. etc. You can't necessarily pinpoint a label on kids at this age (not that they ever should have a label pinned on them), but you can get a feel for their particular bent.
Secondly, this is the time to get kids started on their basic learning skills. Counting. Printing. Adding and subtracting. Spelling. And most importantly, reading. At this age, such skills develop in spurts and have varying ages of onset. Group instruction -- where a child is made to feel inadequate compared to others -- or where a child is forced to rehash skills they have down solidly to the point of stripping all the joy out of them -- is a no-no. Teach skills through games, play activities, one-on-one casual teaching moments, the way good parents already teach. And just let each kid advance as far as they can, as quickly as they like. Make it fun, low-pressure, and geared toward their learning styles, and they'll fly through the basics.
Finally, one of the most important goals is that kids come to see learning as exciting! Fun! They WANT to dress up like ancient Egyptians and learn about how to make a mummy! They WANT to catch butterflies and draw pictures of them and categorize them by color and size. They WANT to hear the story about Gulliver and the Lilliputians. School is A BLAST! There is no set curriculum to be covered at this age, information-wise. The teacher simply works with the kids' interests and plans activities to engage their curiosity. Sometimes in the "home/classroom", but often out in the real world. (Each teacher will need a van and a bus-driver's license to transport his/her own students around to where the action is.) A positive attitude toward learning is far more valuable at this point than "covering" a prescribed amount of material.
The teacher and parents together will decide when the child is ready to move on to Grammar School and a slightly more structured environment. I would expect that would be at approximately 7, but age is not the issue. Readiness is.
And, by the way, I would expect that ultimately, a lot of parents would decide to skip this level and "homeschool" their kid until Grammar School. And that would make me very happy. :)