To be considered a competent reader of a standard newspaper you need a 6 years of education in English, while only 5 in Spanish. I understand Japanese requires 9 years of school for the same feat (I'm don't know how to verify this claim, but it seems reasonable).

There there is a very real cost to not mapping spoken and written languages: kids need to spend more time in school learning basic reading skill - time that could be spent either learning something else, or playing.