I agree with Sandman. He gave great advice.
Kindergarten is a learning experience for little guys and is often the first school experience. It isn't usally set up to expect kids to sit at desks for long periods of time or anything. But in that setting, a teacher can compare your son to others his age and judge his developmental level. I would work with her on any issues in the classroom and be supportive of what she says. He could just be young developmentally or this will be a pattern repeated each year in school. But working with the teachers and counselors is key in solving problems.
As far as differing parents, it does sound like your husband was having a bad day. We have two boys that are a year apart in age---- 5 and 4. Both are wild men and my oldest has a developmental delay called sensory integration disorder that can make him a handful. His brother follows suit. My husband has made comments as well that make me very defensive. What I've done in the past is told him how I feel and that comments like that hurt my feelings for our kids sake. I remind him that they need us to be their fans and how terrible they'd feel if they knew he said that. He usually acts adequately contrite. We don't always agree either, but I try to respect what he feels and he does the same for me. We still don't always agree---- but I we get where the other is coming from. And we try to not do it in front of the kiddos. They hear everything!!
Anyway, good luck. I do think it is a long day for a 5 year old to go to school and daycare (knowing that families must do what they must)--- but he is as tired as you are at the end of the day and then some because he is working very hard in this new school enviroment. Make sure he is getting lots of rest and try to up his physical activity.
I'm guessing that your husband doesn't deal with elementary school kids. It's a whole different breed. I spent 17years in elementary school and 19 years in middle school and kindergarten and 1st graders still scare the **** out of me. (sorry).
Point being, you are right. Another thing to remember is that at this age - what you do at home won't carry over very well to the classroom (in terms of discipline). It really is up to the teacher to be aware and stop the situation before it happens. Now, things that happen at home that are similar to things that happen in class, can be worked on at home. If the behavior can be stopped at home, it will stop in school.
Typically, when I hear of a kid pulling his pants down, my first question is, " ok, who told you to do it." I wouldn't make that big of a deal of it, except to say. don't do it again. He may not even remember why he did it. Unfortunately, he got a response. Hopefully, he doesn't feed off of that.
Having said that, "not paying attention, not following directions, and goofing around when she is trying to teach" are also classic ADHD behaviors. They also happen if the teacher is new, the child is new to a school setting, something is troubling the child, etc.
With both of you being educators, it is tough coming home from the classroom. You are probably both exhausted and hopefully that is one reason why your husband went off. Hey, wait till your daughter is 14 (the tales I could tell). Point being, let your teacher make the decision if your child is a monster. Ask her opinion. If normal measures don't work (and remember, its very difficult for a kindergarten level child to carry over "to do's' from home to the classroom), then you will need to start looking at other reasons for his behavior.
And yes, it is super important that you and your husband are at least in the same book as far as dealing with your kids. Just don't make any fast decisions. Hey, see if he can get a day off and visit your sons class.. As long as you and your husband talk about what to do (even if one of you don't quite agree), and you don't talk about it in front of your child, and do it on a united front. And more importantly do it without anger and do it with love - your son will get the right message!