To sign “school” clap your hands together twice in front of your body, with one palm facing up and the other facing down (rather than sideways as usual when clapping).
To sign “teacher” place both hands at your temples in a flat “o” shape (all fingertips resting on your thumbs) and pull outward away from your head as if sharing information.
Find more school-related signs at https://mybabyfingers.com/staging/9114/sign-of-the-month and practice your ABCs at https://mybabyfingers.com/staging/9114/asl-abcs.
I hope you and your children have had a smooth start to the school year. I now have two high school students! New experiences every day.