I think that you need to be a little more assertive! Sweetly explain to
the teacher that you have your own system of discipline, and as you are
the one giving the grade you have to do what works for you. "Thanks, for
the suggestion, but I have always found it to work this way for me."
Is the teacher staying in the room while you are there? Politely ask her
to plan somewhere else!
Also, have you spoken with your administrator about what time you should
be stopping at the end of the day? If your schedule says go to a certain
time, then I would think that is what is expected of you and you are
right, they should pack up before you get there.
I wouldn't let the interuptions bother me too much. I guess those
specialists have a funky schedule to contend with too! However, you could
question them as to why they are coming in unnanounced. Surely they must
know ahead of time when they will be coming.
Hang in there, there are things to be learned from Art-on-a-cart. You
will learn to be super organised! It's interesting to see the kids in
there own environment, too.