Is anyone here familiar with Goldman-Fristoe Test of Articulation 3?

DS7 has been getting speech therapy all year. At first, the therapist was pretty sure he'd improve after just a few sessions, but he hasn't. So now they decided to do a full language assessment--partially because his speech isn't improving much and partially because we requested acceleration next year.

He took the GFTA-3, the EVT-2, and the PPVT-4. On the EVT and PPVT, he scored 135 and 139 respectively. But on the GFTA, his score was 45, or <.01 %-ile. Now, I know his articulation isn't great, but it doesn't seem *that* bad. His "sounds in error" are r to w, th to s, and sp to s. However, most people can understand him in context. They're setting up an IEP meeting. So... how valid is this test? And what should we be doing about it?

The GFTA-3 is the standard formal test of articulation used by the vast majority of qualified speech and language pathologists. Unless there is reason to believe the administration was not valid, there is no obvious reason to doubt the validity of the instrument itself.

There are various levels of speech intelligibility that SLPs look at for functional impairment, including intelligibility in known speech, and in unknown speech. The former is essentially what you describe as somewhat functional for him--when the listener knows the general topic, and can thus scaffold for articulation errors in the speaker by using her own inferential reasoning. Until one has intelligibility in unknown speech, though, one is not truly communicating clearly and independently.

I would give serious consideration to the recommendations of the IEP team.

We will definitely be starting speech per the SLP's suggestion. However, if his speech is really in the bottom .1%-ile of kids his age, I'm wondering if we need to seek out more help or testing for a possible underlying cause.
He is able to communicate with his teacher and his peers without great difficulty, so I'm not sure how much more to investigate the issues beyond the therapy offered at school.

Among the other avenues that might be worth pursuing, especially if you see other functional concerns, would be occupational therapy evaluation, as quite often, challenging articulation difficulties are related to oral-motor sequencing/motor planning deficits, which may be part of a more generalized dyspraxia.

He has handwriting/fine motor difficulties too. The school OT gave him the Beery VMI test, and he scored VMI: 93 %-ile, VP: 99.9 %-ile, MC: 30 %-ile.
They're recommending weekly OT sessions and a laptop for him to use in the classroom.
The OT noted significant small muscle weakness and suggested it might be the cause of the speech difficulties too.

Good to hear your team is on top of it. One other area that might be worth investigating, perhaps in a couple of years, is dental. I have also seen some students with severe cross-bites and other orthodontic issues improve significantly in articulation after orthodontia. (Not a dental professional, though, just my anecodotal observations, and feedback I've heard from SLPs.) For example, a (2e, actually) student who had both orthodontic issues and motor dyspraxias, with extremely intractable articulation issues, who saw noticeable functional improvement with many years of OT, and with orthodontia (speech therapy, too, but that didn't really spur as much progress alone as with the other therapies).

His dentists have never said anything about orthodontic issues. We had his tonsils taken out last December, and I was hoping that would help some with his speech, but I think it actually made it worse.

Meanwhile, he took most of the KTEA today. He was testing for four and a half hours (with several breaks in there). He didn't finish all the subtests yet, so I don't have official results, but the tester said he got to seventh grade questions on both math subtests and eleventh grade questions in reading comprehension.

He's seven, with a late August birthday, so very young for second grade. Lol

From what the tester said, I think he's going to score higher overall than DD8 did last week...

And this is the same kid whose kindergarten teacher told me, "You can't expect him to be like [DD]," when I told her I was nominating him for the gifted program.