DS recommends the Legal Cheek 'Virtual event series for sixth formers considering solicitor apprenticeships'. Link
Although it says sixth formers, I think it is too late doing it in Y13, so would aim to do it in Y12 (if DC is considering Law at that point). Mainly because a number of the firms open and close their applications (for a Sep start) before the event happens.
The first two events, already happened, of the series are not on the website (at time of this), and are an intro to Soli App, and then Application Masterclass. The latter had some good insight into what the firms look for in an application, and this should apply regardless of the size of firm (even if the smaller ones don't do online tests and/or assessment days).
Would also recommended DCs start thinking about legal (or any) work experience early in Y12.
Not all firms (small or large) do it, for one, some firms don't advertise they do it, and it gets booked up quickly.
The firms said it was not essential, but it gives another strand of evidence, and it may also confirm whether Law/Solicitor is the right route.