If your teen is at a crucial point in their education moving them to another school could impact their school results negatively. Could your child see out their education in your home country by staying with a family member?
You might also consider allowing your teen to stay home with family if you feel that moving them could have a negative effect on their mental health. They could spend school holidays and summers at your expat location instead.
If these options are not available, do what you can to ease negative feelings. Pre plan trips home, discuss the move with your teen and their expat school to see what options are available in terms of certification and try to arrange for their friends to visit.