Sarcastic 12 year old

Hello, I am a new member. I have a son who is 12 and in 7th grade. My son is very sarcastic with me 90% of the time. I am constantly telling him to turn it off, to be serious and sincere sometimes. But he continues! What can I do? I admit to being sarcastic myself and joke with him alot. However he knows when I am being sincere and talking to him normally. Is it my fault, what can I do? I have many issues with his attitude, school performance as well. Any thoughts, advice, support is appreciated. Thank you!