How to make Yearly Curriculum

These day I spend lots of time making yearly curriculum for my Hagwon. I'm still struggling with that.
I have had many concerns. At first I thought education can't be standardized since each student's learning ability is different
there's no need for such a standard program. While talking my head teacher in Hagwon, I realized we need a standard curriculum as a learning objective on which I can teach my kids based. Since I'm a homeroom teacher of most of "lower"(?) or basic classes,which of course seem not to learn fast, I thought I have to change the curriculum to fit into my Ss. There might be a danger of downgrade them.
Considering curriculum standardization vs. customization how should I make balance or should I prioritize either?