If you son is not required to register as a sex offender or if he served no time, things should be fine. If he was a first time offender and received probation under deferred adjudication auspices, he has only an arrest record once he completes probation. If he's of school age, the district might be required to get a court order and access files beyond the arrest.
I would suggest you seek legal counsel (there are free legal services to answer questions for folks that cannot afford an attorney). Not having the type of information you need makes me think your son had a public defender. Public defenders only handle the actual charges against your son. Had you hired an attorney, he would have answered all the questions concerning your son's future. a quick search online shoed lists of pro bono attorneys in Texas. I'm sure all states have such services.
There too many factors that come into play with your issue and I understand your reluctance to ask questions on a public forum. If for some reason you cannot seek paid or pro bono legal help, you can always write a letter to the Office of the State Attorney General if you have questions concerning the implications of your son's conviction.
Pro bono attorneys in Texas:
In my college days, a couple of us were busted for smoking pot. After my probation was successfully completed, I joined the military and passed a background check for a Secret Security Clearance.