These training sessions happened almost every week and students were made aware of their weaknesses and how to deal with strong enemies.
They were getting stronger at a ridiculous pace, however, none compared to the growth rate of Hiro and his team.
Hiro and others are always competing with Rank-S opponents and one mistake would cause them to get knocked out. Therefore, the rate of mistakes made by them greatly decreased as they trained with Professor Mia.
While they could obviously not win against Professor Mia, they did get better and lasted more rounds as the training went on. Though it was all because Professor Mia had limited her strength.
If she used her Ice Palace or similar skills, they would not last one second against her. But that didn't mean that she was going so easy that they were able to think that they could win. She always showed an overwhelming difference between them.