Child residence verification (for schools)

[Dustin Beam]

So this is the second time I've been asked this, so it may be common for school districts in my property's area. Not to mention, I know that the school district divide is very, very close to my property.

Anyway, I have a tenant that previously lived there with her child. She got married and I'm guessing her wife has a child also because I'm being requested to provide a letter stating that the two children live there. She told me she had a spouse moving in, so that's not an issue. I also don't have problems if a new child moved in too.

My question is whether or not the tenant simply telling me another child is there is enough for me to write a letter about it? This doesn't seem like that big a deal to me, but don't want to get into any "trouble" by overlooking anything. 

I don't have any reason to distrust this tenant BTW, just wouldn't have any idea how to verify a child is living there or not.