I would highly suggest you talk to the science teacher you mention. Ask him if there is a time you can get together and talk. Tell him how interested in science your DS is, tell him the kinds of sciency things he's been learning on his own, and pour on the truly-felt flattery about how much your DS loves him and how you feel that you'd really like to encourage a mentoring relationship between them. I don't know if it's proper or not -- anyone? -- but perhaps he could be a paid (or unpaid) science tutor for your son.
Also, totally agree with you on filling in the gaps. He'll clearly have no problem doing it IF there are gaps, and you're right that they advance students at the end of every year who have gaps in their knowledge.
Wish I could be more help!
