If you are in England, it's crazy but the Speaking & Listening stuff with AQA board does not count towards your overall English Language grade. Bonkers, because as a teacher it is a hard enough sell as it is, but it's more difficult to sell to students when it doesn't contribute to the grade, even if, as I tell them, I have never had a job (in or outside education) which did not involve speaking to audiences of people.
In Wales, WJEC board make Speaking & Listening 20% of English Language, over two tasks. Increasingly, we are asked to video (not audio) presentations so the exam board can check (on a sample) that our marking is not too generous.
Regardless of exam board, what can parents/carers do?
You all know this is an important skill. Link it to the idea of an interview for a job or course.
Speak to your teens. Regularly. Actually, not to, but with. Ask them to express an opinion, and then back it up. Keep them talking, because to get a decent grade, they need to be speaking for minutes, not seconds.
Get them to think about how they might speak to someone quite important (ie the examiner). It's a real world skill - if they turn up for any interview and speak as if they were talking to their mates in the park, how impressed will the interviewer be?
Hope this helps.