MOST new teachers have a personal advisor/mentor to guide them during the first year or two. Find out who her's is, and request a conference with BOTH of them AND the Principal.
I agree with the other postings here. It's hard for new teachers. (I know...I AM one!) They're still using the "Ideal Models" they learned in school, and haven't quite grasped the REALITY of a classroom yet.
Meanwhile, try giving your son multi-step directions at home, such as "Go bring me a fork and three spoons, and two napkins." See if he can do that kind of complex "follow directions." Don't scold him if he made a mistake during this test. Try another one, like three yellow crayons and one blue one.
The transition from 1st to 2nd grade is tough. There is a lot more seatwork and a lot less "play". This is complicated by having a mixed group...some OLDER 7 year olds mixed with YOUNGER 7 year olds...they mature a lot during this stage!
If you suspect it's a techer problem, don't be so quick to punish him. Give him abundant praise for GOOD jobs instead. The worst thing you can do is talk about his teacher in front of him!!! This removes any sense of authority she (or any other teacher) DOES have! and sets him up for future failure. (He can always blame the teacher!)
I hope this helps shed some light on the situation, Request that conference SOON, by calling the Principal's office FIRST. He is ultimately responsible, and is most likely aware of the situation already.
HUGS