Episode 1 seems to try and make the arrest and booking process grittily real, but then allows the kid to sit down with the cops while his lawyer is present, and allow the cops to build their case against him. "Just don't say anything about where you were last night, it's fine if you help them try and determine a timeline and what your motive was."
Maybe things are different in the UK, but it ends up coming across as very unrealistic despite the excrutiatingly slow detail that seems to want you to think it is realistic. They raided the kid's house with swat using a battering ram. They are going to charge him, his lawyer wouldn't allow him to say anything to the investigators. There is nothing he could say for the cops to suddenly think, "Hmm we must have the wrong guy."
Episode 2 was crazy. The victim's best friend attacks a kid in front of the cops and yells, "You killed my best friend!" And no one seems to think this is weird. Even after the kid is evasive and runs from the cops, all we hear is he is being charged with accessory for apparently providing the knife. This is after he confesses to the cop he ran from, but the cop who wasn't there magically knows this and charges and arrests the kid for information she wasn't even there to hear.
Let's not ignore the laughable chase scene that doesn't look like anything more than a light jog, where the cop doesn't have a drop of sweat showing on his near skin tight silk shirt after he claims he hasn't ran like that in years.
But the most ridiculous thing about Episode 2 is the cops go to the school saying they are looking for a motive and a murder weapon. The cop's son hands him a motive on a silver platter and they leave still scratching their heads about where that knife is, and why did he do it? What was the purpose of the son's revelation? Just to call the killer an incel? The cop says the victim was bullying the killer, sounds like a motive, doesn't it?
Maybe things get better in the last half, but it doesn't seem like it.