So my DD (starting Y13) is an actress. Has had an agent since she was 4, trains constantly, has West End, film and TV credits. No drama qualifications at all, not even GCSE. Casting want to see what you can do, not what pieces of paper you have.
Until your child is 18, it's going to be down to YOU to manage everything as they won't deal with U18 except through a parent. You will need to apply for agents on their behalf, deal with agents/production, chaperone etc. It's not so bad after Y11 is finished as they can attend auditions alone, but it's a lot of work, and turnarounds for tapes/auditions can be 7-36 hours. Lots of cancelled dinners, trips, parties, events as tape or audition has to take precedent over everything.
This is not an industry where a 16/17 year old can do ANYTHING themselves, it MUST be a parent.
The biggest issues you have:
a) Spotlight: U18s can get Spotlight just by having an agent. Over 18 you need credits - minimum 1 Equity contract, or 2 paid named speaking role jobs. Or, a Spotlight qualifying course - drama college degree is the main route. Without Spotlight, almost no decent agent will even bother with your application.
There are 30k represented kids on Spotlight and maybe a few hundred roles a year. Teens are dead from 14-18 as they will cast an 18 year old whenever possible because U18s need chaperones which is £££ for production.
b) College. No agent is going to be interested if you can't work, so college banning professional work until end of Y13 means you're pretty much screwed with regards to getting an agent until 18+ which means needing either paid acting roles or drama college in order to qualify for Spotlight.
It's a very expensive hobby/job. Spotlight is over £100 a year, then headshots are £80-£500 a year depending on who you use. Self tape equipment: backdrop, lights, mic, editing software. Travel for auditions. Training costs - singing/dance/screen acting/stage acting: £££££
My DD has been reasonably successful. She is not pursuing it as her plan A, but keeping it as a sideline - but she has a top tier agent, credits and experience. She still trains every week.
If there is ANYTHING else your child wants to do, do it.