The first stage in a prosecution is the issue of an’Information’ which is but a formality when submitted by the police but more likely to involve a Hearing before Magistrates in the much rarer cases when submitted by an individual with a view to a private prosecution.
Had the matter gone to trial there was probably a significant possibility of the Headmaster deciding to plead ‘Guilty’ – he could hardly deny that the incident had taken place.
As to the boy having to be excessively rich . why would this be so? It would surely be most unlikely that costs would be awarded against him!