A "Gov't issued ID" is sufficient for U.S travel. A school ID qualifies.

We just got back from flying from PA to Florida and back with our 12 and 9 year olds. They did not need any kind of ID.

we used a copy of their birth certificate

We have never needed IDs/birth certificates/etc for our four kids while traveling domestically, and we've flown on several different airlines.

we also have never had to have any type of id when kids are under ~18 for us air travel- for our own kids or our kids' friends... it probably is different if they are traveling alone without parents/adults...

Thanks all. We did end up sending the passport as DD8was traveling with grandma and we did not want any confusion or concerns. Turned out be a good thing to have an ID as in San Francisco airport, they did ask for a an ID.

GW, I think it might be different if flying with someone who appears not to be a parent of the child. We've been flying to/from San Fran-DC for 14 years with our kids (dh is from San Fran) and have never used IDs. Our kids don't have them. When in doubt though, it can't hurt to have something, though we have never been asked.