I don’t think that’s necessarily a good plan. That will lead to kids pushing harder than they need to on these runs to keep “improving”, but they will absolutely suffer in the 5k because they aren’t doing the Vo2Max and threshold work needed to run a good 5k. At the end of the summer you guys are going to feel like you are sprinting running at 5:00-6:00 mile pace in races and you’ll go lactic way too quick.
Improving easy pace doesn’t improve your fitness, it’s the other way around. I know a guy that never broke 18 in the 5k despite feeling like it was necessary to “win” on all of the easy days and hit 6:30-6:50 miles all of the time. All of the kids running 7:30s to 8:00s on our easy days always ended up beating him in actual races. Some by minutes.
A better suggestion would be to keep the easy days easy, no pressure to hit any sort of pace, and then have a fartlek/short interval day along with a tempo day where you focus on improving week to week either in volume or pace.