Simplify the following text for a Grade 5 native English-speaking person.
Original: Crawford , born in the east end of Sunderland , was a keelman until 1786 when , aged 11 or 12 , he joined the crew of the Peggy at South Shields as an apprentice .
Simplified: He trained as a keelman until 1786 when he joined the crew of the Peggy at South Shields as an apprentice . He was still only 11 or 12 years old .