What Is a Proper Taper?

Hello, My 16 year old has been swimming 3000-4000 yards 5x week on the local team for the past 5 months. (This is after a year out for shoulder surgery, and a year of swimming prior to that. His shoulder is doing fine.) He has 6 months until high school varsity swim team tryouts in August. High school workouts will be 6000 yards 5x week beginning in August. I want to plan his training to both peak for his varsity tryout in August, and to be acclimated to the increased yardage. I know nothing about swimming tapers so I'm strictly guessing. Roughly I thought he might begin now adding 1 - 6000 yard workout a week say for the first month, then 2 per week etc, until in June he can do 6000 - 5x a week. I would guess that July he would taper in some way....maybe: First week 6000 yrd 1x, 3000 4x Second week 3000 yrd 4x Third week 3000 yrd 2x Fourth week 3000 yrd 1x Your advice is appreciated. Thank you!