I'd agree with Cassandra - that's an interesting exercise, going through old yearbooks and making a tally!
In my rural USA community, people started getting braces in 5th grade. The local ortho (who came to town 1 day per week; he also had offices in other small towns) liked to start by pulling the bicuspids, putting brackets on the 4 upper incisors, and using a covered wire back to molar bands. At sleepovers, those girls were also wearing cervical headgear at night.
Kids continued to get braced over the next several years, peaking in 7th or 8th grade. Most wore metal brackets for 2-3 years, followed by upper hawley retainers and bonded lower lingual retainers.
No exaggeration: Probably 80% of my classmates went through this treatment, more or less. I never saw anyone with a herbst, or with any kind of functional appliance, until I found sites like M's Mouthwear!