It makes you crazy if you do. Don't be afraid to talk to the teacher. We really are on the same side. Don't wait for the teacher to call you. I have 120 students and that is a relatively light load.
Most secondary teachers have a lot more kids than that.
I have very limited access to a phone and even less time to use it. So bug the teacher and get in touch. If you suspect there is a problem, there probably is and the teacher is dying for you to get involved. Read to your kid. Show an interest in their school work.