If you can get access to an iPad   try him out with the speech recognition in Pages and Notes (No training, no mic,  no clunkiness and free!) simply make sure the device is on line and click on the mic icon to the left of the space bar .Try a sentence or  two at a time and see how he gets on with it  before investing in Dragon.

You could also look at Splash! Senior to support recording in maths, as well as Clicker Docs Plus which is designed for older learners.  The app "Snap Type Pro" enables learners to photograph work sheets and fill in responses etc on the Ipad.

Try the suggestions on the TechAbility page about writing using voice.   Also you could try the webinar recording on the same topic with other suggestions. The webinar is free to access but you need to give your email or log in using google/facebook etc.

We have Dragon working well in quiet situations and are moving on to trial it with noise cancelling microphones in classrooms. The obvious issue with any voice to text

One warning for windows based solutions - check your school network - we moved to a thin client approach a couple of years ago so all the software sits on the school servers rather than on each individual machine. Saves the IT team days every year with updating things. However, it means I can't buy anything other than a site licence from some providers and that mans one piece of software for one or a few pupils is suddenly £3k plus.

Also worth noting that the license for some of the software covered all windows versions but NOT ipad which is actually separate software so a different licence required for each!