a 15 year old should be able to do anything including fixing full course meals. What helps for my kids to get their chores done is to have an expected chore list written out everyday. It is usually 1 or 2 things a day and doesn't seem overwhelming for them when they see that everyone has duties and isn't targeted at just one person. We also have a very busy schedule. 16 year old is in college and honor classes so has more homework and study time, he mows 5 lawns and works a job 2-3 days a week, is on the drama team and very involved in the church youth group but he also manages to find time for chores and video game/tv time for himself.
13 year old is on drama team, goes to youth outings 2-3 days a week.
8 year old isn't as involved as they are but he does play in sports part of the year and has to go with me as I am also involved in several things every week and work part-time.
one day I might have down
16 yr old. clean a bathroom, sort laundry
13 yr old. clean a bathroom, wash dinner dishes
8 yr old. take out trash, help fix dinner, wipe down counters and table after dinner.
another day
K mow lawn, do load of laundry
S fix dinner, sweep and mop floor
B take out trash (daily chore) vacuum
other chores they do, dusting, folding clothes, put clothes away, clean out vehicles--trash, vacuum, dust with armor all and if weather is warm wash the outside but usually take to carwash when needed.
Keeping their rooms clean is a daily thing and is not considered part of extra chores. If they aren't clean and I have to clean them, I will charge them money to clean so they usually keep their rooms up.
We alternate chores around so no one gets burnt out on doing one more than another. Sometimes they don't get the table that clean depending on how messy dinner was but I usually end up cleaning it again before or after the next meal so it will get good and clean by the next evening meal. I usually don't have to reclean after the older 2 with that though but sometimes have them reclean the bathroom floor if it wasn't clean enough but if bathrooms are cleaned weekly then they usually don't get that bad to need any recleaning done.
We all work together with the laundry as it seems to be the hardest thing to keep up with a family of 5. that helped a lot when I got sorting bins with 6 different bins to sort them by so now when a bin gets full to the top they know that is one full load of laundry and to wash it first. Sorting laundry is a daily chore as there is a full basket daily.
With teens it's hard to always get them to do things so having it written out daily seems to work well for us.