Does an IQ of 70 make me retarded?

I did an online IQ test (BBC one) and my IQ score was70, most websites say an IQ of 70 means your mieldly retarded. But i go to a selective acedemic private school and get good grades, and i have absolutly no social problems at all. Im a 14 year old girl and borderline dyslexic by the way. Am i retarded?