It depends on your program.
Straight out of high school (6 year programs) will typically be younger.
Graduate entry will have average age 24-25. Youngest in my class at UL is 21 and the oldest is about 48. I'm 26 myself. There is also a difference in life experience, so someone who has been out of school, with a job, a mortgage, maybe married, who knows may not like to be grouped as a "kid".
Something to be aware of as a potential health professional - communication is everything. This isn't to sound snotty, but it's a gentle reminder that you're entering a profession where every word does hold weight. It's a learning process (and I'm still learning it as I make my way through patient history taking and clinical exams).
Steele makes a good point about the language differences though. While "kid" is the same, there are LOTS of words that I've had to adjust to as a Canadian to the Irish meanings. I actively switch words when I remember (getting better at it) because the same word can mean something COMPLETELY different - from innocent to not.