By all means, do call the teacher and set up a meeting if you think that would help.
I concur with the suggestions made by dgraab below.
Let us know how you do.
Bette J. Freedson, LICSW, LCSW, CGP
Clinical Social Worker
JustAsk Expert http://www.singlemomsos.com/index.html
To get the most accurate answer to your question, I suggest contacting your son's teacher, principal or the school district. If the school is located in the United States, you can research the school and district phone numbers in SchoolFinder: http://www.education.com/schoolfinder
At my daughter's elementary school, there is a legend on the report card that explains what each grade number/score means. If you did not receive a report card, or the report card you received did not have a legend explaining the scores, please follow-up with the teacher, school or district to learn more.