Toddlers crying while going to the school is probably one of the most common things so don’t worry about it. He will get used to it soon. This might also help https://community.theasianparent.com/q/any-good-ideas-on-how-to-make-your-little-one-sit-still-in-the-car-seat-i-have-one-very-active-boy-who-refused-to-be-confined-in-the-car-seat-haha/868?d=ios&ct=q&share=true
will outgrow, needs time to get used to it