Why is my son all of a sudden not doing good in school?

Our oldest son is almost 14 and is in 8th grade and he has ALWAYS been an A-B student and never had an issue in school. We moved last year and we kept him in his old school as long as we possibly could (till gas prices made it impossible) it was a 35 mile drive one way. Ever since we transferred him to the local school we have noticed a drastic change in one his math class. It’s the ONLY class he literally isn’t turning in his assignments his grade is a flat out 0 for this quarter alreadyand he finished last quarterwith a 60 (only because he turned everything in the day before the end of the quarter to be graded for a late grade). I am able to check his grades and I do. We are constantly on him about it. We communicate with his teacher regularly as well (she has had him stay after school to help him even) he does his homework. The issue is he is supposedly loosing them in his locker. His exact words tonight were his locker is such a mess he doesn’t know where any of it is even. I’ve emailed his teacher to see about setting up an actual meeting to discuss the issue in person as well instead of just emails. I’m just completely lost on how to remedy this and get him back on track. When dad asked him what the issue was tonight he said he didn’t care. I honestly feel defeated like switching him schools wasn’t to best option. Any of you mama’s have any tips or ways I can get through to him.