In the end, all of them decided to forget about the idea. They did not want teacher Fiona to become their enemy. But one thing was that right now they will not challenge him. Even though they could challenge him, it will be a complete waste of their time. Not only that, but they also did not want to challenge him when he was naturally weaker than them.
If they really challenge him and are able to win against him, then it will make them bad in front of everyone. They already reach the peak mortal grade, so if they challenge Allen right now, it will only make them a villain. Because of this, even though they were really interested to know about the process that helped Allen become that much powerful, in the end, they decided to forget about challenging him.