How do you encourage your 4year old, who is having a hard time coping in school lessons because of being forced to skip two levels by the school, to study and have fun with learning?

The best way for anyone to learn something (kids, teens, adults) is to incorporate lessons into things they actually enjoy and make them seem less foreign to them. Or present them in a way that it's not purely theoretical.

Think of how you can make the learning process fun. Avoid adding too much pressure on the child as it may stress him out and baka mas ma discourage lang siya.