The trouble with this model is that each child's learning style, maturity level, and developmental stage is not taken into consideration. Individuality is sacrificed for the progress of the group. The truth is, an individual may be very bright, even gifted, but simply may not be ready to read at six -- or even seven or eight. My older daughter loved to read independently at six years old. My younger daughter wasn't ready to read until she was almost eight. Today they are both avid readers, reading several books a week. Thankfully, homeschooled children do not have to adhere to the "at this age he must be doing this" mentality.
This doesn't mean homeschooled parents ignore reading if a child does not appear ready to read independently. Reading should always be an essential part of your life as a homeschooler and you should read to your child every day. It just means that you do not have to judge your homeschooled child by traditional school standards. It is more important for a six-year-old to develop a love for stories and to see books as a source of information and pleasure. By comparing him to other kids and testing him, there is a very good possibility you'll take away that enjoyment and have him join the ranks of so many kids who see reading as just another subject or chore to get through.