The beginning of the school year is often thought of as a 'fresh start.' However, if your child was struggling in school last year, and no changes have been made, then he is likely to repeat the same struggles, and perhaps the same school year, again.
Instead of waiting, try to schedule a meeting to talk with your child's teachers or counselors, either very early in the school year, or before school starts. This way, you can identify early interventions that you can take, whether it is testing for a learning disability, extra tutoring, help getting organized, or if he has ADHD, a change in medication.
There are many reasons why children struggle in school, such as lack of motivation, attentional problems (ADHD), learning disabilities, behavioral problems, stress with family or friends, being bullied, depression, etc. And many of these conditions can overlap, for example, a child with a learning disabilities might struggle in school and then develop poor self esteem and behavioral problems or depression because he is doing poorly. Or problems at school can begin with an underlying depression or behavioral problem.
Sorting out the cause of a child's school problems can be difficult. Among the resources where you should look for help include your child's school, with a meeting with his teachers, counselor and/or other school personal, and his pediatrician.