Here are a few examples of high school mathematics teachers who have made small changes to their practice which have been positive for both the teachers and their students.
I highly recommend exploring other posts on these blogs.
On exit slips as practice (and giving less homework)
On using individual whiteboards (for individual work and group work)
On using large whiteboards: (to increase the amount of collaborative learning)
Aside: an old post of mine on sourcing large whiteboards in BC
Bonus blog posts:
On showing your working in math Is Your Own Math Work Shareable?