Cohort pacing.

The pack runs on one rhythm and never deviates from it: Concept Day → at-home work → Experiment Day → at-home synthesis → the next Concept Day. Your job as a guide is not to invent a schedule each week — it's to run that loop cleanly, watch where students stall, and decide when the cohort holds and when it advances. This page is how to do that across a room of students who will not all master at the same speed.

The week, as you actually run it

Each unit is a sequence of these two-day cycles. The two contact days carry the live work; the two at-home stretches carry the load that used to eat class time. The split is deliberate — the bench work and the conversation are the parts that can't be outsourced, so they get your time.

Hold this rhythm steady and the variability you manage week to week is mastery, not logistics. The cycle is fixed; how far each student gets through it is not.

When to hold, when to advance

Mastery-based progression means the standard is fixed and time is the variable. A unit is done when it is demonstrated — not when the calendar says so. That gives you two decisions to make constantly:

• Hold a student when the upstream concept isn't mastered. Advancing a student who hasn't cleared the prerequisite doesn't save time — it spends the next unit's time on a gap that compounds. (Use the concept dependency graph to see which gap is actually blocking.)
• Advance the cohort when the majority has demonstrated and the holdouts have a concrete re-attempt path. You do not stall fifteen students for two. You move the front of the room forward and run the re-attempt as a parallel track (next section).

The split cohort: fast and slow in the same room

The realistic case is not a synchronized cohort — it's a room where some students cleared the unit on the first attempt and others need a second pass. Handle it with three moves:

1. Extension, not acceleration, for the fast students. A student who has demonstrated early goes deeper on the same unit — a harder variant of the synthesis, an open-ended measurement, a peer-explanation role — rather than racing ahead into a unit whose prerequisites the cohort hasn't reached. This keeps the cohort together without holding anyone back intellectually.
2. A standing re-attempt slot. Build a recurring block where students who got a "not yet" re-demonstrate. It's not remediation theater — it's the same standard, attempted again, after the specific gap has been closed.
3. Small-group reteach on the actual gap. Pull the holdouts for a targeted session on the one upstream concept the graph flags — not a re-run of the whole unit.

The multi-section scheduling guide has the room-level mechanics for running these tracks side by side when you have more than one section.

What "behind" means — and how to tell a parent

In a fixed-time course, "behind" means a low grade. Here, time is the variable and the standard is fixed, so "behind" means this student needs another attempt to reach the same bar everyone reaches. That is a fundamentally different message, and parents need to hear it framed that way:

• Lead with the standard, not the calendar: "The bar is the same for everyone; your student is taking one more cycle to clear it."
• Name the specific gap, not a vague deficit: "The body-plan basics from sponges, cnidarians and worms aren't solid yet, and the mollusk-and-arthropod work depends on them, so we're closing that first."
• Give the re-attempt path and date: a "not yet" is never a dead end — it always comes with what to fix and when to re-demonstrate.

A full year, with slack built in

Eight units fill a school year at roughly three to four weeks each, with the three in-person demonstrations slotted at the natural seams. Do not pack the calendar to the edge — the re-attempts are the model, so the calendar has to have room for them.