Is it normal i was told i looked like a schoolgirl at work?

I was working at my local pub, it usually has regular customers in and some new customers, and one of the men quite likes looking at me - which is kind of flattering because he's not a bad guy and he has a good sense of humour.

So because it was a Saturday night, I dressed up a bit, I had on a white tunic top (v neck reaching near my chest) that had a little black and white ruffle and went to mid thigh, bunching in a bit at the waist and a bit snug above the waist, but loosening near my stomach. I also had on black jeans and black boots - and I thought I looked quite presentable.

This man looked me up and down - and I could tell he was doing that - and then after a short while, he told me that I looked like a schoolgirl, and I was genuinely speechless, and the local customer next to him was quite surprised.

I'm just curious, was it meant in a sexual way (he is over twice my age) or was it meant as a compliment, or was he saying I genuinely looked too young?