It depends on what you mean by tutoring. Tutoring=preparation; for some tutoring=paid someone to prepare child; for some tutoring=prepared child myself (e.g. by a parent). Some 'tutoring' is done in private preps.
If the question is do children pass the exam without preparing (and by that I mean no stuff on VR or NVR in school, nothing on exam technique, and nothing beyond the learning on Maths and English, that they do in the classroom everyday), then I would guess that in 99.5% of cases the answer is probably no. But in fairness, how many people would consider it wise to sit an exam with zero preparation? It doesn't matter how bright you are, it is advisable (and indeed, in my view good discipline) to prep for an exam.
If the question is do you have to pay to prep for the exam (and that includes paying for private primary schools that do some prep), then the answer is no. However, you do need to have the sort of relationship with your child that you can sit down with them, and get them to work towards something, and then get them to do practice papers or homework. You also have to have the time to do it.
I would say that is why some parents (who are able to) outsource the prep element to an external tutor or tutor group, or to a private primary, or to a combination of the above.