He is young. You call him "spirited". It's early in the school year. Read him the riot act (what you expect - what you won't tolerate and "talking back" falls in that category.) At this point, he's trying to figure it all out. He may be a child that has, just recently, realized that his "high-spiritedness" gets him some attention from his peers.
Just keep monitoring it. Keep that line of communication open with him, asking him open ended questions, like "What was your favorite part of the day?" "What part of the day was challenging?" .... and yes/no questions, like.... "Were you a good listener today?" "Did you pay attention and follow directions?" If you ask him daily questions, you'll get to know your son's pattern of his day, by his responses. Don't take it as a deficit from your son. Just work with your son and keep that line of communication open with the teacher. Roll playing with your child, to help him understand what is acceptable, will help. Getting those phone calls from teachers are never fun. Immediately address them with your child, however, the first one can be construed as a warning for your son - he's pushed the parameters and now, you are on alert. ANY future calls should come with consequences (you don't have to come up with a punishment, yet. Just the mere fact that, should another call come, "consequences will follow" should put a kid, with a conscience, on guard.
You just have to instill in him that, he is expected to act appropriately in school and this is part of life. To be a strong member of the family, good behavior is expected. If you see that he needs something more tangible, then develop a school/reward chart, as a last resort.
And, yes... I can honestly say that I have NEVER received a call from a teacher or Principal, for my daughter, who is now a teen. As far as my tween son..... hmmmmm?????? I love your word "spirited"! Yes, my son can be "spirited", as well. Not rude, or unkind, just, well... spirited. We have a rule in my home that I abide by... "if my child gets in trouble, but I hear the (whole and accurate) story from their lips, they will not get in as much trouble. It keeps them honest and, although they are still in trouble, I lessen the consequences.