Of course we collect necessary info from each student, and advise them of certain requirements, but there are no rejections. Unless there's no form submitted
What we do is set forth a service requirement (ours is 10 hours): Show up at the team carwash in September, show up at our fundraising events, show up at shop cleanup, etc. No exceptions to the 10 hour rule, failure here is that you're not welcome on the team. For those laggards who are eternally late, we do offer some make-up sessions doing the 'dirtiest' work, like carrying supplies, wiping down machinery and tools, taking out trash...
Then we have performance reviews - one at the end of week 2 and one at the end of week 5. Students are rated on productivity, seriousness of purpose, and effort (to name a few). The week 2 is to put the slackers on notice, and the one in week 5 determines if they travel with the team or not. The standards can be as low or high as your team leadership likes, but there MUST be a rubric (score sheet) so all students know exactly what is expected of them.
Just like a real job.
(This system contributed to our winning 3 Entrepreneurship awards so far this year)