Is a young man considered an apostate if he misses the 'Isha prayer due to a physics lesson, knowing that he did not intend to miss it and will abandon the lesson?

"Whoever delays prayer beyond its time due to studying does not become an unbeliever (kafir), but he has committed a grave sin. He should have sought permission from the teacher to pray on time, or intended to combine Maghrib and Isha prayers as a delayed combination (jam' ta'khir) due to necessity. Repentance erases the sins that preceded it."