How was forgetting about exams a question? To Dakota is was an almost certain occurrence until right before the exams when he would realize how bad failing would look. Naturally the opposite could happen, though in those cases he was intelligent enough to prevent such a notable occurrence. Dakota said " Were only fourth years, not like they count." Of course when it came to grades Dakota was probably the last person one wanted to take advice on. As his were average, not an exact middle grade but whatever he figured was the average of the class.

He did not understand why someone needed two brooms or what advantages having two would give him. Either way he decided to just go with it and say nothing just nodding to Trent. It at least made more sense than two different brooms.

Would students do that?

Hopefully not. Even though without a bribe if it looked like Trent could use a little bit of help in trying out he knew he would give his friend the advantage. Which would likely result in much the same result as if he had been bribed. At least Trent went his backpedaling logic of his housemates would think to highly of themselves. His housemates confidence was something that could certainly lead to their downfall. Even more entertaining was the fact that Trent was blushing a bit.

Probably best to let the topic drop. Especially since Trent was continuing on smoothly talking about his brothers. Dakota said " Naturally, though if seriously injured the house elf is important. As some of my cousins at least don't have much of a time sense." Naturally as he said this he thought of one his littler cousins who topped the cake for not having a concept of reality. A thought that almost made him want to cringe considering the crazy little girl would be starting next term.

He had to get those thoughts out of his head before he ended up heading towards the kitchen to grab a tea cup before his little soon to be first year cousin insisted all of them were placed somewhere for some massive tea party. Dakota said " This year really is ending soon. " Which meant he probably should not just forget about the exams.  Why did Trent have to bring them up?  Well besides the fact Trent was probably studying right before coming here for them, thus they were already on the other Slytherin's mind.

off-hand answers are often rather deceiving.
as there is usually a reason they were not washed away