Frank, joe, tony, lee, and bill spend most of their after-school time together fishing, hiking, and playing in their neighborhood. in view of this, which term best describes their relationship?

The answer is "they are a  group".

A Group is various individuals or things that are found, assembled, or classed together. A group is an association of students, friends, ordinarily at a secondary school, school or college, who share a typical foundation or intrigue. Student groups might be administered by an individual from staff, yet are ordinarily sorted out and gone to autonomously.