I used to dread sports days at school. Yes, I went to school in Australia and was a January baby, and started school when I was just five, while my classmates would turn six that year. My mother, to her credit, worried that I was too young to start school, but my kindergarten teacher assured her that I would be okay. She wanted them to keep me down in Year One, but my teacher said that I was fine for Year Two. I remember, when I was in Year Three, a teacher, who would be my teacher the following year, asked me what year I was born in and I answered, and she said, "You can't have been born in that year!" "I was, though." I always competed against kids a year below me at school.
I remember, when I was in year Six, we were playing a sport of boys against girls (I HATED THAT) and the teacher said, "Underarm to the girls and overarm to the boys," but, to his credit, he said, "Underarm to Peter," to compensate me. My primary school PE Teacher used to also, to compensate me, get me to help with setting up equipment.
What those who scream about transwomen in sport forget is, it's not as easy to transition from male to female as it is to be a racing car driver for Holden who switches to Ford. You have to put up with stares from members of the public, being intentionally mis-gendered and the like.