If you want to incorporate the double threshold sessions, with HS or college athletes: Monitor the sessions until the runners internalize the paces and their associated effort levels, because you will get injured if you’re young and try to push through the intervals.
Also: don’t do them by distance, do them by time, so 5x6 minutes AM, and 8x3min PM.
In an ideal world, you’d use a lactate meter between reps, but assuming that’s not available: AM/long interval session is slower than PM - by how much will vary with the ability of the athlete, but: someone running 2k in 6 min for the AM, would run 1k in 2:50-ish for the PM.
The significant thing about the double threshold sessions is that they’re targeting a maximum allowable lactate level at the end of a repeat while it doesn’t translate too well, Marius Bakken, from whom some of this originated: you should never have acid in your legs. “Syre i beina” is a Norwegian means of saying significant and/or felt onset of lactate.
Note that the Ingebrigtsen base phase is supremely frustrating to a runner. The double threshold days feel much too easy, and you do them every Tuesday and Thursday.
The payoff is long-term, because you can do a long, uninterrupted base phase on comparatively high mileage without injury. Forget keeping in top shape for an indoor season, or to abuse your athletes for NCAA athletics. This approach is there to develop athletes beyond college.