Is he shy with girls, or does he mix easily at school with both boys and girls? Is he in a mixed sex school? Does he have any activities or hobbies where he can mix with girls; drama or music are obvious candidates.
Today, for most children in primary and secondary schools, mixing with the opposite gender is completely normal, and relationships are often relaxed and not considered 'any big deal'. Unlike my own junior school in the '40s, which had a separate boys' playground, away from the girls and infants, and I grew up imagining there was some dramatic reason why boys and girls needed to be kept apart.
I agree it could just be 'experimenting', wanting to know what women's clothes 'feel' like. (I am male btw.)
I have worked with teenagers in schools, and many do claim to be sexually 'aware' and some 'active' but as a TA or voluntary helper (I have been both) one cannot normally know how much is bravado, or wanting to keep in with their peers. Many older teens were not shy to talk to me about drink, drugs, sex, porn etc, (just in general conversation). Some boys, for instance, would frequently draw cannabis leaves in their 'jotter' books, though I can't recall pictures of a sexual nature. (Perhaps they wouldn't want me to see that; but they would often ask inappropriate sexual questions.)
Perhaps many girls and women do not realise how difficult coping with puberty, sexual interests and desires can be for shy or insecure boys.