Last week of the academic year often brings this sort of injury at school. I've had similar other physical injuries throughout the year, and every year before.
I love my job, but the children need the holidays. I'm physically shattered. I've been sleeping for 10/11 hours a night for the past 3 weeks.
For me, the exhaustion comes from having to mentally be on the ball throughout the 7.30am-5.30pm working day (10-20min lunch and toilet stops if you can squeeze them in). Physically be on the ball, as you're on your feet most of the day. Emotionally take care of yourself, as you're managing the emotions of 30 children, their parents and all that life has for them including deaths, illnesses, job losses, abuse, mental health, family fallouts etc. And schools are now doing so much more in the way of social work than we ever had to.
And that's before you even consider the planning/assessments/reports/data/migf forms/SEN needs/G&T needs/working at needs/managing your team of staff.
Schools used to be primarily places of education. Now we're primarily places of care-but with higher than ever expectations of education. Children starting school in nappies (when no SEN needs) and not a clue how to even hold a book is a real thing.
So yes, it's exhausting. Most physically exhausting jobs are just physical. Most mentally exhausting jobs are just in the brain. Teaching has the perfect storm of needing to daily be on your feet at the coalface for 30 people AND their families 8.30am-3.30pm.
Then fitting in all the additional work that has to be done at some point in the rest of your day. Which is often 9pm onwards, as you've got your own family to love and support when you crash through the front door at 6pm.