Phineas and Ferb: The Last Day of Summer What Happened after it

Not to much is known of wha happaned after that, except that know Phineas and Ferb have different classmates, and one is Irving. Perry the Platypus appears now in school, secretly, to help Phineas and Ferb on something, and as Phineas and Ferb, and the gang promised, they wont tell anyone Perry is a sceret agent. Phineas and Ferb impress children in school for their creative skills and where announced as the student of the month, multiple times. They also became the center of the class. In the other side, Phineas is know dating Isabella, such as sharing food with her, and even talking about what they like, and going to restaurants to kiss and eat, and they even eat spagetti, where they kiss after they eat the long line of spagetti together. Otherwise, people are sending cards and letters to the nationwide, saying that Dr. Doofenshmirtz is dead.