It's going to be pretty inconsistent for how I will write them.

K: 154cm (5'1")

Sayaka: 160cm

Marvelous: 5'9" (He looks like a 25 year old so I have to improvise.)

Carl: 144cm

Ashlynn: 163cm (no wikis stated what her height is but it stated her age. She's 18 years old in Xrossedronpa.)

Ren: 175cm (5'9")

Roy: 173cm (no wikis stated his height. He is 16 years old in Xrossedronpa.)

Yuga: 143cm

Maria: 133cm (no wikis stated her height. She is 9 years old in Xrossedronpa.)

Franziska: 162cm (5'4")

Vivia: 196cm (6'5")

Ruby: 5'2" (1.57m)

Cloud: 173cm (5'8")

Flora: 5'6" (no wikis stated her height. She is 16 in Xrossedronpa.)

Marinette: 135cm

Kanade: 145cm

Tallest: Vivia.

Shortest (if we ignore the kids): Marinette.