The kind that go on the actual toilet, does your 4+ year old still use one? If not, when did they stop using it?

My oldest is almost 4 and she still uses her potty seat, she is so small it makes it a lot easier for her. She can use the toilet without out, but it makes it harder for her to wipe. In public I just hold her on the big toilet, but I know at school she just uses to regular potty, but they are smaller toilets. I guess I'm just curious when kids ditch the potty seats!