Thanks guys (gals) for your responses.
Well funnily the kid came out to one of the 5 people I have told I am trans.

She's someone I work with, not just a random person at the school which is why she told me. He's also in my class 3-4 hours a day.
@Spacial--It's what I have heard, that some number of kids are gay. I have always heard this and lately have thought it was unlikely. I also "came out" as trans at age 7. I recall it quite well. I didn't change my mind either. Esp not a kid who would say that he was born in the wrong body, which is almost a trans stereotype.
There's another reason for the pronoun. If I start thinking "her", I could "slip". I already did that once. The kids did not like it. And I don't want zer teased (more than ze is). I am sure I was thinking how trans I thought ze was. I am not likely to slip with zer as it forced for me, but even if I did it wouldn't be understood.
@Arch/henrytwob- Yeah about the parents. I have worked with LOTS of Latino families since moving to NM. They have great family bonds but being socially liberal is not one of their virtues, let's just say. Sure there are exceptions. But I wouldn't want to take a chance.
@taka others-- I think the whole thing of letting the kid know I know others who are trans and so on is a good tack. I don't even have to necessarily get the teacher to tell the kid to tell me. We talk about stuff like the word "gay" used as a slur. One reason to tell where I was is that that kind of discussion is actually encouraged where I live, vs some places where it might be frowned on.
They gave us a pamphlet on "What to do when the kids say 'gay'".
BTW, I know lots of trans people in real life since I go to support groups and hang around at the trans center.
--Jay J