How old of a four is she? I'm not sure what you're using with your five-year-old, but couldn't your four-year-old do the same? I started my DD at four years, four months this year. We're working on the kindergarten/first grade level. She's done extremely well and have been totally surprised and delighted by all that she has learned and can do. As a side note, we just started the second half of HOP Kindergarten today. Having said that, we spent a month or so cementing her letter identification and sounds before starting the first half of the program.