Yep, that is a much better system.
Infant= 1,2 (age, 5,6)
Primary= 3-6 (7-10)
Secondary (HS)= 7-11 (11-15)
Is just daft.
I prefer the junior high/high school system, but that could be just because that’s what I had in Virginia in the 1980s.
As for ages, they can start 1st grade at age 6, which means a student whose birthday is in the summer (like mine) completes the final year of secondary school at age 17 and turns 18 before starting college in the fall.