Hey, Kevin! Thank you for the response. Arguably, you may be ignoring the final clause of Section 505:
[A]n alien who is not lawfully present in the United States shall not be eligible on the basis of residence within a State . . . for any postsecondary education benefit unless a citizen or national of the United States is eligible for such a benefit (in no less an amount, duration, and scope) without regard to whether the citizen or national is such a resident.
True, a Texas resident is eligible for in-state tuition, but an Arkansas resident is not eligible unless he establishes residency. Only if an Arkansas resident could qualify for in-state tuition without regard to whether he was a resident might Texas plausibly under Section 505 offer in-state tuition to illegals. In 2005, a federal district court found that plaintiffs did have standing to sue with regard to their claim that a Kansas statute granting in-state tuition violated Section 505, but because there was no private right of action under the statute, their suit could not proceed (Day v. Sebelius, 376 F. Supp. 2d. 1022 (D. Kan. 2005)). I am frankly not up on subsequent court cases.