Were you told that from a parent? I'd say yes if that's the case and if it would stop you from having sex at such a young age.
However, the answer is no. I've never heard of something like that. I'm sure that just by having sexual intercourse, your hormones won't stop you from growing... Instead they'd help your growth. (But I'm not saying to go out there and just have sex)
No, just the opposite. You're grown alright - a young person suddenly saddled with an "adult" life. Your carefree childhood, fun, reputation & youthful opportunities will be lost. Not to mention possibly making a baby you cannot care for now. Wait a few years. It's so worth it to not rush growing up. It comes too quickly & ends too soon.
Don't do it; you are a child. That's just wrong. And no, whether you do or not doesn't affect your physical growth NOR does it make you any more mature. In fact, sleeping with someone when you are that young shows great immaturity and short-sightedness.