Cool! Here I am!
Let’s go to childhood
The little Nicolas
Leaves school

I am the kid
From your childhoods
Or maybe the childhood
Of your memories
Chalk dust
And map of France
Paper balls
On blackboard

Yep, makes only a little more sense in English than in French (I speak fluently)
The second line suggests that he is about to leave school (at least for the holidays) to go enjoy ‘childhood’.
The second stanza sort of lists typical childhood objects in the classroom (at least at the time of writing).
Hope this helps, please comment if there is anything else you don’t understand and I will answer.