You in a Petri Dish is the second stage in Spring for Sensei.
Strategy 1 (sort of cheese)
This stage can be very easy if you have Awakened Bahamut Cat. All you need is him. DON'T spawn anything else as they might trigger Ms. Madonna to attack and release a Shockwave, damaging your Bahamut. Wait until you have enough money to spawn Bahamut, release him, and Ms Madonna won't be able to create Shockwaves because Bahamut will knock her back. Don't worry about Teacher A., Bahamut should be able to finish off the base before he becomes a problem.