Background
I'm a Team Lead for a software development department and about 4 months ago I began aggressively spearheading an internal program to hire and train up junior developers, specifically focusing on candidates with other real-world experience looking to make a career change into software development but with no experience in software development. We administer objective tests looking for characteristics we believe act as markers of high potential in software development (abstraction, symbolic math, etc.), do interviews, check references, etc.
I ended up hiring a junior (our second) who is acquainted/friends with some members of our department (myself included) who met all of our requirements, based on the idea that he'd integrate well; he passed through the tests very well and came with good references, shone in the interview with people who didn't know him, and everything was great. Since I'm in charge of the Junior Development program I tasked him to studying using Treehouse, Microsoft Virtual Academy, Pluralsight, etc. and gave him access to our corporate account for all of these resources - I never made any progress in these things formal parts of his job duties, but absorbing this information in a timely manner keeps him on the curve for our achieving our base functional level for promotion to associate within a year. Additionally, myself and the other members of the team regularly pair with him and generally make him "drive" while we navigate, in an effort to pass along information in a practical context and give him an opportunity to ask questions.
The Problem
Despite our best efforts to help him learn, giving him additional resources to come up to speed, and flat-out asking what he needs we're not seeing any significant improvement - to the extent that I'm skeptical if he is actually using the educational resources or not. He regularly neglects to use resources to look up problems and asks us about trivial things, or worse, head-butts the situation with brute force until he gets frustrated and quits paying attention; part of this may be that because he isn't learning the fundamentals he should be picking up from educational resources, we think he might not have the context-knowledge of how to search for what he needs.
To compound this, lately we've noticed he drops his attention much easier and starts messing around with his phone or otherwise getting distracted, either while we're "driving" during a pair to show something complex or when he's running a build (takes 15 seconds to complete the build, but he spends 5 minutes on his phone), and his phone goes off CONSTANTLY throughout the day, causing context switches. These seem minor, but 20-30 times a day between builds and phone buzzes ends up eating quite a bit of time; it's as though he thinks that being a developer gives him a free pass to mess around since it's not "real" work (my perception, not sure about the veracity).
I'm not sure how to get through to him that he needs to focus and put more effort into his learning, AND pay attention while at work. My goal is to be understanding and professional, so I want to find an intermediate step to show that I'm serious about him needing to shape up before going to an extreme like a PIP or a formal write-up.