The big accountancy firms, consultancies and systems integrators often offer formal schemes for people who are taking a year off between school and college studies. These would give you an insight to what it is like to work in a professional services environment and may give you connections that make it easier to find internships or jobs with the same firms later. The downside of these schemes is that you will be inculcated into a very particular way of thinking about and doing things, and particular culture, which may not be amenable to being a "good consultant".
In my opinion, you would be better to get "hands-on" experience in a smaller business as it will enable you to:
A: develop a more grounded and balanced view of what makes clients' businesses successful (hence how, as a consultant, you can help them)
B: get a broad view of business careers before committing/being sold on a consulting career. There are good reasons people often move into consultancy later in their careers - it helps to have hands-on experience of the things you are advising clients to do.
C: start developing an idea of what sectors and functions interest you - this decision is as big and important as the decision about whether you want to work in consulting or industry
If you have an opinion on the sectors or functions that interest you, this is a good time to explore those interests. In applying for jobs as a "gap-year" student, I would recommend being clear about your position. If you have your acceptance to college for the following year, put that on your resume along with your SAT scores. This will help make it clear that you are a "graduate calibre" candidate available for a high-school graduate price - a strong offer to recruiters. Also be clear about the areas you are interested in, and your willingness to do relatively menial work (as a junior consultant, you will often find yourself doing very similar tasks anyway, so there is no point being precious). Much of the benefit of this year will come from being exposed to how decisions are really made, how organisations really work, and how work really gets done. Should you decide to move into consulting, you will find that understanding vital.