We don't need longer school years. What we need are better teachers. We need more funding to hire better qualified teachers that are able to engage the students and turn them on to the material being taught. Most of my teachers were boring and came across as not being interested in their own lesson plans. If that changes, our performance levels will change.
What we need, essentially, is to instill a love of knowledge and intelligence into children and to encourage them to question everything they hear or read.
That is partially what I meant when I wrote "... and turn them on to the material being taught."