It is so true that 10 or 12 was fairly young for role of "page" or "clerk"
but maybe not for person place and time. i did do a double check on the doc used for age of Alonzo. Take a peek

Milledgeville was the State Capitol from 1804-1868, so Mr. Slater would have been a youth, no more than 10-12 years of age during his term as a "Page".