You can hit F2 to reroll the entire map before you begin the first halt. I do this a few times until i see several medium and large halts.
I re-roll like a slot machine because RNG games like this or Slay the Spire will give you better runs then others. if your pupils have terrible traits there is no need to try, reroll and get a more useful batch. Saves a lot of heartache.

There is also a trait that a pupil can have that prolongs the amount of turns you have on every halt.