Proud mother of a 17 year old son here who has never answered me back, never thrown a tantrum, never got in trouble at school.
From birth all he did was eat, sleep and fart. When he started school he never cried or got upset, he just ran in and sat on the carpet.
Puberty was uneventful apart from hilarious going to bed one night squeaky and waking up the next morning with a voice like Brian Blessed.
He studies hard, is polite and seems to be well regarded by teachers. He also has plenty of friends, likes to party, have the odd beer, enjoys sports and music.
In fact both of my boys are unusually placid.
Once the 17 year old did slap another kid in the face (I was mortified because it was next door neighbour's son), but the vicar's wife witnessed it and declared that that DS had been pushed to the very limit of his patience and if he hadn't done something then she might have!
Another time a kid tried to start a fight with him during football (my DS is rubbish at football - he fluffed a pass or something, huge upset - footballers seem to get very emotional), other kid kicked him in the back so he just turned around, picked the other lad up and threw him on the ground before walking away. Again the PE teacher witnessed and said that he was sorely provoked.
Don't worry that placid means weak or feeble. Placid can be calm and strong and full of self resilience.
Of course now I have bragged about my silent and placid giant it will probably all go tits up....