Marti's link contains the following info also. From
http://idea.ed.gov/explore/view/p/%2Croot%2Cstatute%2CI%2CB%2C614%2Cd%2C2%2CC%2C .
(I) Transfer within the same state.--In the case of a child with a disability who transfers school districts within the same academic year, who enrolls in a new school, and who had an IEP that was in effect in the same State, the local educational agency shall provide such child with a free appropriate public education, including services comparable to those described in the previously held IEP, in consultation with the parents until such time as the local educational agency adopts the previously held IEP or develops, adopts, and implements a new IEP that is consistent with Federal and State law.
(II) Transfer outside state.--In the case of a child with a disability who transfers school districts within the same academic year, who enrolls in a new school, and who had an IEP that was in effect in another State, the local educational agency shall provide such child with a free appropriate public education, including services comparable to those described in the previously held IEP, in consultation with the parents until such time as the local educational agency conducts an evaluation pursuant to subsection (a)(1), if determined to be necessary by such agency, and develops a new IEP, if appropriate, that is consistent with Federal and State law.
In other words, for an in-state transfer, the current IEP is in effect until the new sd reevaluates. There's no guarantee they would find him eligible.