The Animorphs went through so many disgusting experiences. How jaded must they have been when the time came for them to dissect frogs in science class?
Cassie: would be surprisingly zen about the whole thing. If anyone asked why she was so chill with this waste of life, she'd point out that the frogs had longer and higher-quality lives than any of the chickens in the nuggets served in the cafeteria. Plus, this is hardly her first (or hundredth) time seeing a dead animal, given her dad's job.
Jake: would be sitting next to Cassie in silence, handing her the scalpel and accepting the liver and lungs from her as needed. Wouldn't be paying any attention at all to the unit.
Rachel: would be fascinated, and would ask all kinds of unhinged questions. So that's why when you stab someone in the lower abdomen they bleed out of the nose, and oh the way that you can kill someone by driving skull fragments into the brain makes so much more sense now! Rachel's lab partner is edging away down the bench by the time she's finished delightedly noting down on the worksheet that you could probably kill a frog — or a hypothetical 6'-tall frog who was shooting at you — just by removing one of its limbs with sufficient force.
Marco: would be doing that thing where he's quietly disturbed, and loudly making jokes to cover for it. He'd be imitating Kermit with the dead frog as a mock puppet, using a bad French accent to critique the meat quality, kissing his frog on the mouth and then wailing "Prince Charming nooooo!" when this has no effect, and generally making himself a giant nuisance. He can't suppress the obnoxiousness reflex, and anyway... it's just a little guy. It didn't ask for this. What a way to go out, gassed and then pinned to a board in 40 different pieces. And he's definitely not thinking about that thing Cassie said about the chicken, no siree.
Tobias: would like to note that he had no idea those were frogs meant for a science class. Has every intention of suing the school for the massive stomachache he got from swallowing so much formaldehyde.