Does anyone remember the Bailey School Kids series?

[Cynthia Hanson]

Does anyone remember reading the Bailey School Kids book series? I remember reading them years ago. They were about four third-grade kids getting themselves involved in a mystery about whether or not a certain grown-up who either came to work at their school, or took some position in their city was an actual creature or classic character from either fantasy, sci-fi, or horror. The endings were always left vague but I always suspected they must have been.

I've been digging out my collection of these books lately and was wondering if anyone else has read them and what was their favorite books in the series.