The fun thing about an IEP is, it's supposed to contain only things that are actionable, demonstrable, and measurable. "Provide more challenging materials in specific areas" does not meet that criteria. It's too vague.
Knowing that gives you an opening to begin a dialog with the school. Something like, "We're reviewing DS's school activity with respect to the IEP, and we have some questions. We're not sure what "provide more challenging materials" means" (because you already know it means practically nothing). "What materials are being provided that are not included in the standard first-grade curriculum? How often is this being provided? What grade levels do these correspond to?"
That ought to set off some red flags in the school that you know about the accountability requirements of an IEP, and you intend to see them enforced if necessary.
The gifted science pull-out sounds like it's an enrichment offering. Those are designed to be on grade level, and related to the grade-level lessons currently being explored in the classroom. Honestly, I don't know what else you could do about "textures" within the confines of a public school. The simple answer is that enrichment isn't nearly enough for your DS. He probably needs acceleration.
