At the meeting, the teachers should ask your son to tell them what's getting in the way of his performance, and help him to come up with strategies for getting around these. The school can do you a favor by asking your son what he's prepared to do about his own performance, and get him to sign an agreement about his role and responsibility as a student. They can insist that he come in for after school help, or use the services of a tutor they provide. His teachers should also ask him what they could do to provide him with more (or better) assistance, or what they could do to make school more interesting and motivating for him.
The transition from middle school to high school is a very challenging one. Your son may be so overwhelmed by the demands of his freshman year that he's given up any hope of being successful. Since you said he has LD and ADHD, you all need to make sure that he is capable of what's being asked of him in school and on homework. If, for example, he's impulsive, has a poor attention span, and he's reading like a third grader, then reading a chapter in a tenth grade history book for homework is a set-up for failure. How about books on tape? How about a "study buddy," to increase time on task and motivation? How about having him say how much homework he will be able to do successfully and then evaluate the reasonableness of his prediction the next morning at a homework "check in?" He shouldn't be blamed for having this problem; he should be helped to overcome it. It's part of his disability. Similarly, he shouldn't be allowed to use his disability as an excuse for non-performance. Counseling, monitoring, modifications, and support are critically important if you want to keep your son from sliding down that slippery slope to failure.