How deep did your high school go on complex numbers?

I recall we covered them very lightly (mostly to explore what happens to roots of negative numbers), but we certainly came nowhere near the group theory stuff or linear algebra aspects mentioned in this post.

I’m curious as to how many high schools around the world teach complex numbers. In England in the late 80s when I did A level maths (age 17-18) it was part of the syllabus, but now it is only available in the harder A-level further maths, which is often not taught in the standard non-selective non-private schools, making entry to university STEM courses more difficult.