Sure, but what do they do in grade 4 and 5, after basic arithmetic and fractions? I'd be surprised if the answer didn't involve quite a bit of proto-algebraic "word problems" of the sort described in my comment, and in the attached reference.
In the US states I've lived in students start first grade at age 6 or 7, sometimes depending on the month they were born in, but also depending on readiness, but also depending on what age they started kindergarten or preschool if they did. Kindergarten is nearly universal in the US, hence the K-12 system, and preschool (the grade before kindergarten) is what is optional, and daycare before that. I was 12 myself in 6th grade. So though he seems to be in another country (Estonia), his system seems to me to be similar to the US as regards grade numbering. I am not aware of 5 yr olds in the US commonly being in 1st grade. May I ask what country you are in where first grade begins at age 5 on average?
