1) If you are truly concerned about test scores, consider not looking at immersion schools. There are any number of good reasons why these schools show lower test scores and still do a good job educating children. I won't go into them here, but it is a drag to have tours taken over by passive-aggressive (or even aggressive-aggressive) parents with this bone to pick.
2) Leave a ton of time to find parking if you drive, because you never know how a given block or neighborhood is. You'll need to park for about 1.5 hours, as tours rarely "dismiss" on time.
3) Dress warmly as you will be spending considerable amounts of time in drafty breezeways or outside (earlier in the year, I would have said apply sunscreen as you may stand on blazing asphalt for quite a while!)
4) Keep it down in the classrooms. I am amazed that the teachers can teach through all the distractions people on tour introduce into the classrooms.
5) Take notes, as it all becomes a blur after a while. Consider sharing your thoughts in comments if a school is reviewed. It really helps balance out the reviewers' inevitable biases or blind spots.
For schools with tours:
1) Do whatever you can to have the principal present. It makes a huge difference. It signals a commitment to incoming families, and lets us see your vision for the school.
2) Make sure parent tour guides are really well-versed, and yet also able to defer questions to the principal (another reason it is good to have him/her there). Most have been wonderful, but occasionally a tour guide can really throw things: the best ones convey information succinctly, do not override things with their own issues, and have notes on the facts in their hands.
3) Please oh please make sure that whoever is answering the phone has all the relevant information: what tours are language-specific, the correct start time, and whether or not you need to pre-register. People are taking clocked time off work here, and aren't happy if they show up and find out they are there on the wrong date, at the wrong time, or not on the list.
4) Please know that we are deeply grateful for comforts and welcoming elements like music (yay, McKinley!), coffee (go, Marshall!), expressions of sympathy about this strange process (hats off to many of you), and offers to let us e-mail you (ditto).
And that is all from me. Really.