It very much is against the law. Read to the end. Here's the last paragraph of the article:

According to the law offices of Ned Barnett, Texas law prevents registered sex offenders from working in places frequented by children, including schools, daycare centers and playgrounds or attending school events like sports games. Some can interact with children at family gatherings or public events, supervised when interacting with children according to court orders and the nature of the offense.

This isn't a problem with the law as much as it is a specific group of people trying to wallpaper a sort of compliance with the law while ignoring the substance of it altogether. First paragraph of the article, emphasis mine:

The Texas Home Educators Sports Association (THESA) thought it could get away with allowing a registered sex offender to coach minors by sending parents a waiver to sign, with the coach's testimony attached, according to Amy Smith at watchkeep.org.

Note also from somewhere in the middle of the article:

The waiver mentioned nothing about his offender status.

And if you're wondering wtf, you're not wrong: all this careful arrangement of fact seems like a very creative effort on the part of the author and editor to actively distance point A from point B. It's possible they're just trying very hard not to piss anyone off in what is already a lost cause.

Or to put it another way, in a state with a very high year-round accumulation of snowflakes, this article involves three very special groups of special snowflakes all at once: a sex offender and his personal fans, the homeschoolers, and the evangelical Christians, and how they are faking compliance with state law by making sure the parents sign a waiver -- one that hides the relevant information about a sex offender with a history of minors -- before giving him free access to their children in direct contradiction to the law, a law they knew enough about to deliberately circumvent.