In both drama, students are forced to play a death game against their will with a mysterious admin controlling everything. Eerie and suspensful setting.

Same "Mafia Game" type drama. Students locked up to play the game. Mystery vibes.

Same "Mafia Game" type drama. Students locked up to play the game. Mystery vibes.

Similar plot, students forced to play a death game.

Towards the end of their summer holiday, a group of high school students’ peaceful lives are disrupted. Someone named “Admin” adds them to a chat group and forces them to play a killing game. Before they find and remove “the target”, whose identity is unknown, anyone in the chat group who does not reply to other members’ messages will die instantly. Panic strikes as students in the class suddenly die one by one. Ho Hei Yin, a gentle and simple student, fights with “Admin” to protect his precious friends.

Very similar plot:

Towards the end of their summer holiday, a group of high school students’ peaceful lives are disrupted. Someone named “Admin” adds them to a chat group and forces them to play a killing game. Before they find and remove “the target”, whose identity is unknown, anyone in the chat group who does not reply to other members’ messages will die instantly. Panic strikes as students in the class suddenly die one by one. Ho Hei Yin, a gentle and simple student, fights with “Admin” to protect his precious friends.

The story is very different but :
- They have the same mysterious vibe
- Both have an eerie cinematography style.
- Both are about brothers and their bond
- Both feature a character having visions

In both, a teacher is confronted with their students commiting a murder.
In Confessions, it's the teacher's daughter. She then tries to get revenge.
In Saiko No Kyoshi, it's the teacher herself, and she go back in time to prevent that.

Both drama feature school teachers trying to fix their classroom, sometimes using unconventional methods.

Both drama feature school teachers trying to fix their classroom, sometimes using unconventional methods.

Both drama feature school teachers trying to fix their classroom, sometimes using unconventional methods.

Both drama feature an adult trying to fix a messed up school.
In Saiko No Kyoshi, it's a teacher that manages to go back in time after being killed by their student, while in Ao no SP, it's a policeman assigned to work in a school.

Both drama feature students trying to kill their teacher.
Saiko no Kyoshi is more realistic, while Sensei wo Kesu Houteishiki can be a bit over the top sometimes.