My Hero Academia’s "Joint Training" arc reintroduced Class 1-A's student rivals, Hero Class 1-B. It was their first training exercise with together and both classes were divided into equal teams that were pitted against each other to measure their growth in friendly competition.
All the students were fired up and determined to give their all, with Neito Monoma in particular relishing the opportunity to finally triumph over Class 1-A, but there was no attempt at cheating or any underhanded activities. In fact, the most unsportsmanlike behavior was exhibited by Class 1-B's homeroom teacher, Vlad King, who frequently emphasized his own students' achievements while belittling 1-A's.
Vlad King's love for his students cannot be overstated, and it's not limited to just Class 1-B either. When the League of Villains attacked the UA students at the Forest Training Camp, he put his body on the line to protect the extra lesson students from the powerful blue-flame user, Dabi. His partiality to Class 1-B, while a tad immature, isn't unfounded. Compared to 1-A, Class 1-B had an uneventful first term. Fortunately for them, they hadn't been targeted by the League of Villains yet but during the Sports Festival, they couldn't shine as much as they'd hoped -- much to Vlad's chagrin. Until the Joint Training, many still hadn't even been named in the story yet.
Vlad Sensei's biased commentary was mostly for comedic purposes, but its secondary purpose was to force both MHA viewers and Class 1-A to take a good look at the progress their fellow students had made. The Joint Training exercise was meant for both classes to compare their strengths, identify their weaknesses and perhaps help the hero course students sharpen each other's edges. The screen time devoted to each class was roughly equal, but since 1-A had been the main characters of the series so far, the audience would be subtly inclined to pay more attention to characters from that class.
What Vlad Sensei's incessant praise aggravated some Class 1-A students, it forced the audience to take a more critical approach in assessing Class 1-B's performance. Even though their rivals won more matches in total, Class 1-B didn't give them an easy task of it at all. In the matches they either won or drew, Vlad made sure to aggressively celebrate their victories. In the matches they lost, he critiqued the errors they made, but also pointed out moments of quick thinking or impressive resilience from his students.
For example, during the third match Kaibara Sen was captured by Iida Tenya. As Iida transported him to the jail section of the training ground, he continued to struggle with his Gyrate Quirk, forcing his captor to focus on keeping him in check and significantly slowing Iida down. It seemed like a futile struggle in the moment to all who watched, but not Vlad King. He recognized it was Spiral's continued struggle that prevented Iida from rescuing Todoroki Shoto faster. Had Iida been just one second faster in getting to his teammate, the match would have ended very differently from the draw that it was.
Vlad indeed could get a bit worked up at times, especially when he'd encourage his class members during match beginning announcements and solely attributing Class 1-A's first win to Shinso's involvement. But propping up Class 1-B wouldn't have worked half as well if there was no truth in his exaggerations. Vlad Sensei forced both the My Hero Academia audience and Class 1-A to acknowledge his students and introduced a slew of new heroes who could be counted on even if Class 1-A was unavailable. But like Midnight joked, it was ironic that his Blood Control Quirk couldn't help him keep a better handle on his emotions.