There is far too much ageism on this thread.
I have, I think, 5 colleagues (that I know of) who are in their 60s. TBH, an outsider wouldn't know (well, maybe they could tell with the 65 year old). If I had to guess their ages, I would say early 50s.
No one has any trouble climbing the stairs, or staying on their feet, or controlling their bladders. They are quick-witted and have enough stamina to get through the day and prepare for the next. They worked out long ago how to deal with stress and time management.
Their IT skills may be slightly lacking, but they can do the basics, and they are never fazed if the network goes down. They are wonderful mentors of new teachers. They aren't afraid of speaking their minds in staff meetings, and rarely worry about staff-room politics.
I love our older teachers. My closest older colleague keeps threatening to retire, and I keep begging her to stay.
When younger teachers here say that they couldn't continue working as they are now into their sixties. That may or may not be true. If you want to, you will be a good teacher in your 60s as you will be more experienced than you are now and will have developed a full range of skills to help you.
There are good and bad teachers of all ages. The bad ones in their sixties were probably not so hot in their 30s either. There weakness are not age-related (although they may use age as a mask). You don't automatically become deskilled because you get older.
Not wanting to go to work is not limited to teachers. How many in any profession would work if they didn't have to?