Brainy Charlotte Pain, a straight-A student, has an IQ of 149 – just five points below the former Countdown maths queen.
The gifted year 11 pupil's intellect is within the top two per cent in the world. Only 14 per cent of Mensa members are under 20 – making the achievement all the more remarkable.
Charlotte, who is currently studying for 10 GCSEs, passed a rigorous supervised test session, lasting two and a half hours, to learn her IQ.
She modestly said of the result: "I was really happy and very surprised. I just wanted to find out what my IQ was out of interest. I am really excited about what the future holds."
Aiming high, Charlotte plans to take A levels in geography, physics, chemistry and biology at the school, in Maxwell Road, Northwood, with a dream of studying the latter at Oxford University – although she has no fixed ideas about a career yet.
In her spare time, she is a sailing instructor for disabled youngsters and adults at Hillingdon Outdoor Activities Centre (HOAC) in Harefield, and is hoping to begin a course in deaf studies and sign language at Harrow College.
Charlotte's proud mother, Catherine, said: "Charlotte has always been an achiever and a hard worker at all the schools she has been at, but since she came to Northwood College she has quite literally blossomed academically and personally.
She is a happy, enthusiastic student who has a very strong moral outlook on life. I know she is looking forward to sixth form with great enthusiasm."
Head mistress, Jacqualyn Pain, no relation to Charlotte, added: "We are thrilled with Charlotte’s achievement and are delighted that she is continuing into the sixth form.
"At Northwood College we focus on raising young women who know their own minds and are creative and flexible thinkers, as well as being able to achieve outstanding results.
"We aim to develop, stretch and challenge every one of our pupils, through our unique approach to advanced thinking skills. We think this makes for a more interesting and vibrant school community."