What will it take for an OOS student to get into UT Austin?

My son is a Junior in a charter school in MA. His top choice is UT Austin for Computer Science. I understand that the acceptance rate for OOS is very low there.
His WGPA is currently 4.0 and his school doesn’t rank.
He just took the ACT. What score will give him a reasonable chance (not necessarily guaranteed) to be accepted as an OOS?
He played JV Basketball (Captain) and is on the Varsity team now.
We expect him to get good recommendations.
What else do they consider as key differentiators, especially for OOS?

Thanks

Here are some statistics for incoming freshmen to CNS:

https://cns.utexas.edu/students/future/freshmen#2015-freshmen-class-profile

Due to the fact that almost 80% of the students are in-state, he’ll probably need to be at about a 32 to be considered if he had all of the requisite internships and experiences, with high math and science scores. Also, over 95% of the admitted students were in the top 25% of their class (2/3 were in the top 7% in a Texas Highschool), so good grades in his math and science courses are a must. What is his UW GPA? Is grade inflation pretty rampant at his school? It seems from the bullet point listing that the most important factors besides having great test scores and grades is to have some sort of relevant internship, be calculus-ready (with A’s in math and science courses), and simply write good essays and have an all-around well focused application.

Thanks for the answer.
UW GPA is 3.6. There’s no grade inflation. His school is highly competitive, in fact, ranked top 5 for all schools in MA.
He has As in all Math courses, except for a B in AP Calc BC this year. I don’t think he’ll be able to improve it at this point, but he thinks he can score 5 in the AP test.
He did a summer internship with a startup, working on a tablet app for the medical industry (coding and testing). Expecting to go back this summer as well.

Thanks