The Academy - S3-E6
Plot hole: When Ahsoka rushes to save the students when they arrive to meet the prime minister, she attacks several secret police officers, who flee afterwards. However, we later see her standing next to the prime minister acting innocent when she pretends to side with him. The officers she fought earlier would no doubt have told Almec what side Ahsoka is really on, so her ploy never should have worked to begin with. (00:11:55 - 00:13:40)
Answer: I guess that 1) the King assumed that Ventress' droids were meant to capture the Jedi, not kill him outright. When she yells at OOM-224 to shoot Yoda, she evidently failed that expectation. 2) Sending out a bunch of Droidekas after it is plain that Master Yoda has clearly won is not a sign of good sportsmanship, either.