I have been given recommendation forms that have required that I assign a numerical rating on a number of attributes. Where there is a free form response section, I highlight the good. But that hard rating is unavoidable on many forms.
While I am not a teacher, I have done enough of these that I care about being a credible source so while I will be very positive in the free form section, I would not say someone is something they are not. Fwiw, I suspect the less positive things matter less if they are consistent with how the applicant portrays themselves.
If your son describes himself as someone who throws himself whole-heartedly into what gives him joy and continues to work on imposing structure on himself, this will be a good recommendation. AOs like to see that a person knows who they are. A kid who describes himself as a leader and who is characterized by teachers as quiet and thoughtful is more likely to seem out of touch.