How do you motivate a 15-year-old boy to realize the importance of his education? All that's important to my son is his music. He's good at it. But the struggle on his schoolwork is exhausting. He doesn't care. He has failed 9th grade and is in summer school and really doesn't mind repeating the grade if he has to.
You can't motivate a 15-year-old. He's probably going to be held back and have to go to another school. Make him face the music of what's going on in the class room. It may be a great lesson.
His mother wants him to learn the lesson without the consequences. We have to make mistakes. As Mark Twain said: good judgement comes from experience and experience comes from bad judgement.
The academic environment isn't everyone's strong suit. But remember many people have great careers without having done well in high school.
Keep your eye on his long-term well being. Make sure he has other things that give his life meaning and give him a sense of self-esteem. Luckily, he's already motivated about music. If he loves music and understands the experience of giving 100% he has got what it takes to have a successful career. Maybe it's producing or marketing music.
Being able to do algebra doesn't necessarily mean you'll be successful.