Do you follow dr Becky on Instagram? Her handle is drbeckyatgoodinside - she is a behavioral psychologist with young kids and just did a post on school resistance this morning.
To answer your question, my 4yo is currently very good about it but we def have issues getting out the door sometimes. And last year, his first year of nursery, many days were hard. In fact, until recently I’d have trouble at pick up (in addition to drop off last year.) we have friends who’s 4yos also are sad going to school and I’ve personally seen tantrums happen at drop off.