Figure out whatever it is that the boy likes, whether is in relation to learning/reading or not, and give him a toy in that subject. However, when you give him that gift, tell him something along the lines of this: "What you are about to do, going back to school, learning something new, is _the most important thing_ you could do for yourself. Endeavoring to become the best possible version of yourself is the most noble pursuit for any person. I could have given you an education gift, something symbolizing the path upon which you are currently set. However, I am gifting you something of which I am told you are currently interested, because what we are celebrating here today is you, not just the path upon which you are currently progressing. We are celebrating 'you', and all of that you may become."
Anyway - just a thought, I am still learning how to motivate my own kids and have found similar approaches unexpectedly successful.
{edited obvious typos}
To make reading more something cool and fun.