Separation anxiety?

Hi everyone! My LO just turned 4 last November and is now in K1. There are days where I drop him off in school with no issues at all, he'll be happily skipping his way to put his bag in his cubby hole. But more often than not, he will ask for random things like snacks before he steps in to school and if we tell him we will get it after school, he will start pulling a long face and refuse to go into school. No cryings though, just whining and refusal to step into school and start being clingy to me for 10mins or more. This is quite frustrating especially at 745am. Is this separation anxiety or just trying his luck? Anyone faces this problem and how do you handle it? Grateful for your insights!