Possible Clues:

• Like summer school classes, often
• 9 across isn't finished with Ring losing the head with preventative action
• Designed to address problems or deficiencies
• Engineers face corrective
• Like some summer school courses
• *Call again, on a rotary phone
• Like college courses for the ill-prepared
• Provided for children with learning difficulties
• Aimed to cure
• Romeo emailed boss - it's meant to be therapeutic