Children go through different stages, and sometimes something as a decline in grades can be bigger than just them not doing their homework. What should you do if you noticed your child's grades dropping?
Most the times your gut instinct is correct. You may notice a change in your child's attitude towards everything, especially things they enjoy. They may show signs on not wanting to go to school. Finding out a little more about the situation always helps. And sometimes swift action is needed which may result in even moving schools.
You need to figure out the reason, whether it's because they're spending to much time with friends, or because they're upset about something. Then you need to discuss how you're going to address the issue and, if appropriate, explain the importance of maintaining good grades.
I don't have school aged kids yet, so it's not something I have experienceds. I think I'd start by talking to them, and trying to find out whether there is something going on that's upsetting them, like bullying at school or family stuff, which might be affecting their work. Then I'd look at which subjects they were having most trouble with and see whether I could help them myself or if they might need a tutor.
There can be a range of things that can affect your child's grades from being bullied at school to teachers. It is a good idea to talk with your child to see where the trouble is and to see if you can make some positive changes.
I'd try to find out if there was a reason (not work related) and if not, then get help in that area - whether that be sitting with the child and doing extra work in that subject, or hiring an OT or tutor or whatever.
A drop in grades is usually related to a drop in understanding on a subject. It could be as simple as a child not understanding some basic concept that has been taught in class, and then everything that builds on top of that just becomes too hard. I would sit with my child and go through the basic concepts and words of the subject/s they are not doing well in and find out what they didn't understand. It can be hard for a classroom teacher to get to do this with so many students in a classroom so going over the work with them regularly to make sure they're on top of it can help (not in a forceful way, but just gently to make sure that they understand what they are learning).
I would perhaps think about hiring a tutor to give them the extra coaching that they might in particular subjects at that particular time in their lives. A good foundation and grasp of topic goes a long way.
I think talking to the child first to see if there is anything going on at school you may not be aware of. The next point of call would be the teacher and ultimately the principal. Things can be a little more complicated if a child's parents are divorced and he/she spends time in two homes.