I would really recommend saying to the teacher something like "I hope this doesn't sound crazy but I keep thinking his hair looks shorter. Did somebody cut his hair?" That way it doesn't sound like an accusation and just see what the teacher says. Plus that way if you do go to the principal you can say that you brought it up with the teacher because that's probably going to be the first question anyone asks you - "Did you ask the teacher about it?"
I think you'll always get a better response when the perception is there that you tried to work out the problem before escalating it.

The key to not being "that parent" is tact. I have been my children's advocate for years. I have had to intervene in my daughters school many times before I brought her home to homeschool her. My son on the other hand was having people take his stuff, from mechanical pencils all the way to his homework. I have had to calm myself down, rehearse what I wanted to say, and I also ran the whole speech I wanted to say past my husband before I took it to the school. I have found that if I go to them and talk rationally and tactfully things do change, however I will not let things just be done to my child without bringing it to someone's attention. I guess I am just " that " parent lol . I am ok with that though. Because since I talked to the school my son has been for the most not been having anything else stolen from him.

This wasn't like just a chunk taken out, it's like someone gave him a full haircut. I've calmed myself down, and making notes and measurements, cause like a lot of you said he does have to be with these people everyday. I don't want my attitude to effect his schooling. ANd I admit I get overly protective and a bit snippy when they don't listen to what I tell them about his health/behaviors. We will be transitioning to K in a couple months, so I think I will bite my tongue for now until I can get some kind of "evidence" (for lack of a better word) behind me. Thanks everyone for your responses, they calmed me down and made me feel better.

you are your childs only advocate. YOu have to stand up for him. wether the haircut was intentional by staff or was an act of bullying by another student has to be delt with. chain of command start with the schools counselor. if no results the principle then the board of education. You have the right to make sure this does not happen again . stand your ground. if you don't stand up for your who else will.

I would definitely put concern down on paper, but confront the principal on your concerns and send an email to the teacher. Maybe a kid on the bus is doing it?