If they start wasting their time there I'll take them out, they can work or go to Polytech.
If they are using their time wisely they can stay.
It really doesn't make much sense to go an alternative route unless you need to.
If they're at risk of dropping out and doing more harm than good, get them out of there.
Sincere question: can they work? Does anywhere hire high-school aged kids for work that isn’t non-trivial/grunt work?
If the goal is to not waste their time I can’t imagine working a casual job is more stimulating than being in a classroom. Maybe a year working casually would inspire them back to school the next year?
You learn real world skills, the value of a dollar, work ethic, business processes, and get to build relationships and network with people of varied ages, unlike school.
Plus, you learn the importance of the customer.
I saw a lot of kids go on to higher education only to mostly waste it. They were there because their parents made them, not because they wanted to be there.
I worked for a year before going to uni, after that, I really wanted to be there. Working sucked. I wanted a better job. When I hit uni, I was extremely motivated to learn.