My kids' primary has announced a change from shirts to polo shirts (previously just KS1) for all years except year 6.
I just think it looks a bit rubbish - all the other (in the main more affluent) local primaries have kids that look smart, and ours now get to look like they've just rolled out of bed. My DC are annoyed as they enjoy looking smart at school.
I associate polos in school uniform with young children and others who struggle with buttons and spilling stuff on themselves.
They also wash and wear badly (as stains kind embed themselves in polos) and the collar doesn't sit properly when open so a lot of (KS1) kids wear them tightly buttoned up to the neck, which doesn't exactly seem comfortable.