Simplify the following text for a Grade 8 native English-speaking person.
Original: After leaving school , he worked behind the scenes at the open air theater at Regent 's Park as a prompter , then an assistant stage manager ( ASM ) on a tour of The Merry Widow , and then at Theatre in the Round in Scarborough .
Simplified: He worked behind the scenes at the open air theater at Regent 's Park as a prompter ( helping actors who forgot their words ) . He later worked as an assistant stage manager ( ASM ) on a tour of The Merry Widow .