There is a L6 Chartered Management apprenticeship and, as far as I am aware, a small number of large scale manufacturers and retailers recruit a small number of 18 year olds onto these eg Mondelez, Morrisons, Nestle, Unilever. These are organisations with typically large workforces spread across sites in the UK. There are also some purely project management type roles with organisations like IBM or some of the large construction groups.
Some things to bear in mind:
You must have a credible plan B worked up in parallel (ie uni options) as roles are hyper-competitive. Students with very good predicted grades also need to be absolutely clear about what they are giving up if they decide not go to university.
Academic grades only a small part of the mix and don't have to be stellar. Recruiters are looking at the whole person and candidates able to evidence existing experience of working with colleagues, customers, team mates etc in pressured situations are more likely to succeed.
Many/most organisations expect people to have some domain knowledge or core skill that is fundamental to the organisation and then develop managers after that; this is way the number if truly entry level 'pure' management routes (whether school leaver or grad) is limited.
Recruitment for September 2025 starts can happen at any time from now through to Jan/Feb time. There is no single source of information on these kinds of apprenticeships, so you need to be curious and scavenge the internet. Not ideal but does weed out the less committed you could argue.
The individual recruitment stages can be alternatively very intensive (and sometimes clashing with Y13 winter mocks) or painfully drawn out (and sometimes clash with A level exams), all depending on the efficiency of individual recruitment teams. So be prepared for that.