I’m 15 (UK) and I love acting but I can’t sing. Do I have any chance? Can I get into a drama school?

Alan Chenkin, Learned about celebrities by reading the tabloids at the supermarket checkout line…

I have a secret to tell you, and you may find it disturbing.
Lots of actors can’t sing.
The get cast in musicals, animation, Indie films, and commercials, because of their name recognition, box office, or connections – not for their singing ability.
Many actors and actresses exude such a powerful presence that we believe they are powerful and capable of doing almost ANYTHING.
Here is actor Robert downey Jr.  (he plays Tony Stark aka Iron Man) delivering a bionic arm to a young fan.  Get a good look at that little boys face – that is the power of belief.
Many actors never went to drama school either.  Some have a natural talent, others rehearse excessively, and many auditioned well or have golden connections.
If you HAVE to sing, you must Practice.  A lot.  Get a singing coach.  Find pieces that showcase your talents. Make a youtube video, enlist your pals, entertain at parties, post, tweet, and build your brand. You are on a great journey and you must, MUST! Play this role to the hilt. 
 If you can’t hold a tune, and your singing might clear the room – then you must act, emote, and hone the skills you have so that you can win your audience over.  In the back of your mind, think of those actors who are such compelling performers that they get cast in singing roles, even when they are not great singers.

You can cultivate that powerful stage presence in YOURSELF, and win the audience over!

Ambition, Drive, and good auditioning skills will get you into drama school.
Break a leg. -Alan
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This post is expanded from my original answer in Quora.