12 year old constantly lying!

If she is lying to you, she might not feel safe telling you the truth. It’s also appropriate developmentally for kids to test boundaries and lie. I suggest building trust by not taking things away or punishing her. Try helping her reframe the truth and react safely, no yelling, no anger, no harsh tone. Kids will find a way to lie to get what’s they want sometimes regardless. But if you know she is lying say the teacher reached out and told you she failed a math test try not to approach it where you give her the chance to lie, like how’d your test go. Instead trying saying your teacher told me you failed your test, do you need extra support on your work to feel confident to pass next time? How can we work together to get a passing grade next time. Try to be on her side, frame it as being on the same team. It sounds like you want to see her succeed, kids learn from example too. Make sure you’re being honest and holding yourself accountable as well. Teens are hard but you can change this

Therapy is also an option. Family or individual.

Trust me I know how useless I was for eight years raising a child that wasn’t mine and is a compulsive lier, I had to go to therapy to learn how to deal with him. And now he is going to a psychiatrists, sometimes is not our fault, is just how their brain is wire. Sometimes they just need a little more help.