I currently run Windows 10 w/Fall Creator's update in VirtualBox 5.2.6 on a 2011 Mac mini with 16GB RAM.

If it is an 8GB RAM machine, you may want to caution about running any other applications while using the Virtual Machines, or your son may run out of memory. Your son can run any of these solutions on the 2015 MacBook Pro with El Capitan.

Parallel's Lite (free) in Mac App Store requires $60/yr in-App purchase to install Windows.

Expects a Windows 10 ISO (.iso) installer.

One of three virtual machines to run Windows 10 concurrently as a guest OS with OS X.

Thoroughly read the above link before plunging into a Boot Camp installation.

Apple provides specific drivers for Windows 10 for MacBook Pro hardware compatibility.

One can choose to boot into OS X, or Windows 10.

Creates a separate, bootable (not virtualized) partition on the Mac and installs Windows 10 into it.

Apple's Boot Camp Assistant (included) with El Capitan in /Applications/Utilities.

Your options for running Windows 10 on the 2015 MacBook Pro with El Capitan, are: Depending on the school's business relationship with Microsoft, they may offer a less expensive, and even potentially, a free version of Windows 10.

If the school requires Visual Basic Express, then you need to provide your son with a Windows solution on his Mac. Visual Studio Code is not Visual Basic Express, nor does it recreate the underlying Microsoft Windows system features and libraries that Visual Basic Express expects.

Visual studio free download for mac