I started the year earlier so I finished school at 17 & 5 months.
I didnt bother me about not being 'legal'(I had fake ID) but honestly, I lacked so much maturity going into uni.
I had no idea what I was doing, I knew what interested me but no concept that this would be a career path. Making friendships was hard, and I was really immature socially.
I have a similar issue now with ds1 who should start school 2 days after his 5th bday. I don't think he'll be ready but I also think sending h at 6 would potentially be frowned upon.