Why are most people so short nowadays?

Yea kids are getting taller but....most of the kids I work with are tiny or short. I work with 8-10 year old kids. The kids are pretty tiny. I saw their height chart and most are 3'11-4'3. TINY. The teachers I work with are all women. Three teachers. The three are 4'9-5'4" I'm the big one 5'10. I'm the tallest woman..... well female teacher in the school. There's a 13 year old girl that is 6ft. Anwyays is it just me or is it just because I'm tall? I was tall for an 9 yeat old. I was like...5'3 or 5'5.