I'm considering making homework worth nothing and having their grade be only 2 in-class exams.

When I did A levels and my first undergraduate degree (in the UK) that's how it worked. The only measurements used to calculate my A level grades and degree class were:

- Proctored exams at the end of 2 years of study (the last 2 years of high school)

- Proctored exams at the end of 2 years of study (the last 2 years of university)