Macrons are optional, and it's more a help for us to study, than a real part of the language. But it's an important help, and some Latin texts do have the macrons and other diacritics (apexes).
I really hope they'll add the macrons later, as it's the only mean for us to be able to speak in Latin, not only read it.
I think in Ancient Greek, it has more the meaning of leasure. That's a weird coincidence (I think it's not a coincidence), because "schola" has the meaning of leisure in Greek, and school, or group, and "ludo" has the meaning of leisure and school too.
Ancient Greek "Σχολαί" Plural of the Ancient Greek word "σχολή"(skolè) (from which its Latin counterpart "Scholae" derives), meaning: 'rest, leisure'
https://en.wikipedia.org/wiki/Non_scholae_sed_vitae :) (I just changed schola into ludus, did I get the declension wrong?)
The conjunction "ubi" should be thought of as introducing a verb; it doesn't control nouns, in and of itself.
What's controlling the case of "ludus" (nominative) in this sentence is the verb "est" (is).
Ubi est (+ a nominative-case noun): "Where is (the ... ) ?"
Quo ambulas / curris / vadis , etc.: "Where are you walking/running/going?"
Unde venis ? "Where do you come from?"