Yeah, I also remember this happening to me when I was younger. I think I raised my hand and said here(only start thinking about saying here when the name of the student that comes before you is said). Im, not a licensed speech therapist so Im not sure about proper technique. I would first tell your teachers about it so they knows. Also, I think you might be putting too much pressure on yourself of you having a speech block in front of a crowd of your fellow classmates that could be causing the speech block.