Is it possible to get sniper school in a contract for 11X, or 18X?

It was possible back in the day if you qualified expert, get recommended, and if there is a slot available for privates who completed OSUT as an 11B to get Sniper School enroute to their first duty assignment as a standby if there was a class that was short filled. It was extremely rare, but it did happen. It was something earned by exemplary performance at OSUT and is not something you can get guaranteed in an initial contract though.

NO!

Sniper school is not something that you're going to get in your initial enlistment contract. Meaning that when you go to MEPs you're not going to see it on your contract, now once you get to your unit if you work your way into a sniper section you have the chance.