Fun fact - in central/eastern Europe algebra starts in 6th grade (kids aged 11-12yo), and we don't have much problem with that.

Did algebra in middle school. Southeast US education system. Pre algebra was taught in my elementary school as an introduction.

In the public school I went to up through 7th grade (in the late 90s), the top 10% to 20% took algebra in 8th grade. In the private high school I went to, most of the 9th grade class had algebra the previous year (whether they went to public school or private for middle school). While by no means universal, it's been pretty common for a while.

At least as of 15 years ago in a middling California public school.

7th grade (age 12/13): Pre-Algebra

8th grade: Algebra

9th grade: Geometry

10th grade: Algebra 2 / Trigonometry

11th grade: Pre-Calculus

12th grade: Calculus 1