On Judging Language Levels

I'm still new to teaching, and one thing I'm struggling with is judging the level of students.

My favorite Japanese teacher seemed so adept at speaking to me at my level - not above it or below it. Conversations with her were informative and rewarding. I find that most native Japanese speakers overestimate my Japanese ability, however; they speak over my level, making conversations a bit more frustrating.

I often feel like I, in turn, overestimate the English level of my students, essentially speaking over their heads. Sometimes, though, they surprise me by how much they understand, and I find myself feeling like I'm insulting them by underestimating their level.

It makes me wonder how my favorite Japanese teacher managed to be so perfect! I took it for granted at the time.