When Ender started training with his former launchies (to stop his isolation), how was it effective?

In Chapter Seven, Ender learns by watching Bonzo and the soldiers. He studies the way Bonzo commands, learning both what to do and what to do differently. He also considers the formation of the toons, the subgroups of soldiers in the army (generally in groups of ten with one leader): the toons are too formal, too rehearsed, while more fluidity would give them an advantage.

That night, Ender goes back to his old Launchie barracks to get his younger friends to practice with him. He teaches them techniques from the armies and practices his new skills. Bonzo disapproves but technically can do nothing, so they come to an understanding in Ender's favor, but one that saves face for Bonzo before the other soldiers.

Ender continues practicing with Petra and observes two more battles.Ender notes some of Pol's good ideas, such as keeping his army constantly moving. Ender feigns being frozen, and at the end he breaks his orders, shoots several Leopards, and forces a draw.

Ender continues to remember his launch group, training with them in his free time. Even though the Launchies are so mature for being so young, Ender stretches them beyond what the adults have perceived they are capable of achieving. Ender can teach what Petra taught him, but he also teaches what he has learned on his own initiative. Those who train with Ender have an advantage.