Sounds like you already have some good information about your daughter's performance! First, every school is likely to be different in terms of what is considered below level, on level, or above level, depending on the specific assessments they use, etc. For example, some schools look compare each child's specific scores against the rest of the kids in that class. Because assessment varies from school to school, you'd really have to find out more about the specific assessments and criteria that your daughter's school uses.

However, all of that said, 100-120 wpm is well above any benchmark score or norm that I've heard of for the end of 1st grade - I can't imagine that falling in the below average area for the beginning of second grade. It's possible that a new assessment system is being used, that your daughter is only falling below area in a very specific area, or that the assessments were not reliable (e.g., perhaps they were given in a noisy environment, or by someone not yet trained/familiar with the assessment process). In other words, I don't think it would be possible to derive a score of 100 wpm for an entering 2nd grader and call that below average, so I'd dig a little deeper and find out what assessment was used, what scores were derived, and how they are interpreting those scores.

Moving forward, I would suggest a few things. First, gather any documentation of her performance last year, and be prepared to discuss that with the school. It sounds like you've already done that. Second, gather more information about the assessment process the 2nd grade teacher is using, including specifically what assessments have been used, the scores attained, and the teacher's interpretation of that score. I'd also ask for her thoughts about the data she's deriving when comparing those data with the scores from the previous year. Third, find out what those assessment data will be used for - will it be used to give grades or make educational placement decisions, or is it just informational?

After you gather this information, it may be helpful to post another question, or comment on this one. You'll likely learn a lot some new key pieces of information which will help inform your next steps of decision-making.

Your daughter is lucky to have you as an advocate, and hopefully you'll find resolution in the coming days/weeks!