For lots of reasons, school is a very common trigger for anxiety, especially when it starts or after a break. Getting an anxious child back in school can be rough. The type of anxiety that can be triggered by school can vary. It might be separation anxiety, fear of getting sick, perfectionism, social phobias or fear of panic to name some. (On a personal note, the thought of math class can still make me run in circles and holler.) If you are concerned your child may get very anxious going back to school here are a few things that will help.
Focus on the Right Target
Most people focus on the wrong thing. They try to reduce the anxiety first and foremost. Believe it or not, that is the WRONG focus. The correct focus is do what you need to do even if you are anxious. In other words, be anxious and do it anyway. If you are shy talk in class, stay in the room even if you feel you might get sick, turn in the paper that is bent, etc. The key is to disobey the fear. Then the anxiety will go down. If you focus on reducing the anxiety you are still treating it like it is dangerous. Act as if it is a pest but not dangerous and it will naturally dissipate. One of my young clients worries that his rapid heart beat means he has a heart problem. On his first day of school, his mom told me he felt his heart acting up. Instead of sitting out or holding back he ran extra hard at PE and joined a football game at recess. That is EXACTLY the right approach.
Don’t Escape!
Do NOT avoid. It is easy if your child is not currently acting or talking about anxiety to just ignore it and hope it won’t show up. Bring it up. Your concern is probably that it might cause anxiety right then. You are correct, it will. Treating anxiety is causing anxiety in a structured systematic fashion. The goal is to strike a balance between too much at a time and too little. This is called exposure. This is the gold standard for overcoming anxiety. It is facing your fear on purpose. Here is link with a bit more explanation.
Step-By-Step
Overcoming anxiety is a process. I know you would love a silver bullet, a miracle and a spectacular healing. So did I when my child had anxiety. Seriously, I really did. If you don’t get the miracle then you have to develop a process. For example, if your child is anxious about being separated from you then you need to develop a step-by-step plan of gradual exposure. Start practicing being separated. If the amount of time is a main factor then gradually increase the time of separation; if distance then increase that. It is hard to go from zero to 100 on the first day of school. If you want some examples, search online for “(Name of Fear) hierarchy”. You should be able to find some examples of how to break something into steps.
Once Isn’t Enough
Rehearse, rehearse and then practice some more. This is part of the exposure process. Drive to the school, walk around and if you have access go into the classrooms. Do it as many times in a row as you can. If you can only do it once, make a video of walking around and play that at home. Talk about what your child could do in the classroom if they get anxious. Many parents worry this might cause them to think about anxiety and that will lead them to be anxious unnecessarily. (Refer to point 1). Just realize when you start the exposure process your child will get anxious. This is when you will be tempted to quit. Don’t. Do it again, then again, then again…you get my drift. If they are too freaked out make it an easier exposure but don’t quit when it is hard. Rehearse the kinds of situations that might cause anxiety. If they feel anxious when you talk about it, don’t change the subject. Instead gently help them to just tolerate the anxious and stay with it. It will go down on it’s own if they stay with it. It is not dangerous, only uncomfortable.
Adjust But Persist
When you are developing a plan the difficult thing is to get the steps right. Chances are one of the steps may cause too much anxiety. Don’t stop, adjust. I work with a lot of kids (and adults) who fear throwing up. It is called Emetophobia. My steps are basically words, 
stories, drawings, pictures, videos, sounds, smells in the order. The way I figure out the steps is to start really easy. For example, I will say the words, “throw up.” I ask on a scale of 10 or with kids I have them draw a vertical line and mark how much it bothers them on the line. Top of the line is awful, terrible, horrible and piece of cake at the bottom. If something is above half way then I back off. So if throw up is okay then I use more graphic words like puke and vomit. I don’t move to the next word until the word I am on drops down. It drops when I say it over and over, they say it over and over and maybe we make up a song about it. We write it and say it. That is exposure. It will go down. If the fear is being embarrassed then break it down as well. Talk about it. Imagine it over and over. Find videos of people being embarrassed. Be creative. Use the numbers or lines to discover how hard it is. When kids get anxious they focus on what they can’t or won’t do. Change the focus from that to, “What can you do?” For example, if your child is very shy they might not be willing to raise a hand in class and answer a question. Rather that keep pushing on that ask them, “What could you do that is a little bit hard but not that hard?” Could they make eye contact with the teacher or another student?
ZZZZZ…..
Do not underestimate the importance of sleep. Gradually begin to change from summer sleep habits to school sleep habits. For most families, you should expect some resistance. If you can’t get you child to sleep even if they are in the room then start getting them up sooner. Eventually, most kids will adjust to the new pattern. The lack of sleep causes difficulty in emotional regulation. Someone prone to anxiety will be more anxious if he or she is sleep deprived.