School starts at different ages in this area. For myself,

We went to primary school at the age of seven, stayed in primary school for six years and graduated at the age of eleven.

Then I started junior high school in the second half of the eleventh year, graduated from junior high school for three years, and graduated at the age of fourteen.

Then I went to high school for three years and graduated from high school at the age of seventeen.

So generally speaking, from primary school to university, you don't repeat one grade, and 18 years old should be a freshman.