Tuesday's lesson is decided by what the class got wrong last week. The problem is that on most Mondays you don't know what that was, because the only way to find out is to mark everything, and the marking hasn't happened.
How it works on paper
The set goes home on Tuesday. Some of it comes back the following Tuesday, in bags, in various states. It gets collected, and it sits in a pile until someone has an evening free.
When the marking happens, the information arrives one sheet at a time. Priya got question 7 wrong. So did Marcus. By sheet nine you have a feeling that question 7 is a problem, and by sheet twelve you're fairly sure, but you've also noticed three other things and the feeling about question 7 is now competing with them.
Then you have to do something with it. Question 7 was ratios, so ratios is a problem, so Tuesday should open with ratios. Except that the pile got marked on Sunday night and Tuesday's lesson was planned on Saturday, and the two haven't met. And the three students who didn't hand anything in aren't in the pile at all, so they're not in the feeling either.
That's the Monday morning problem. The information exists. It's spread across twelve sheets, arrives too late, and never adds up to a sentence you can act on.
The sentence you want
"Eight of twelve missed ratios."
That's the whole thing. One sentence, on Monday morning, before anyone walks in. It tells you what Tuesday's lesson is, and it tells you it isn't Priya's problem or Marcus's problem, it's the class's problem, which means it's a teaching problem, which means you fix it once at the front of the room instead of twelve times at the desk.
The second sentence you want is "and two of them didn't open it." Those are your two phone calls, and the sooner you make them the better. A student who skipped one set had a busy week. A student who skipped three is a family that's drifting.
You can get both sentences by hand. It takes a tally sheet with question numbers across the top and a stroke for every wrong answer, filled in as you mark. It works. It also depends on the marking being done by Monday, which brings you back to the pile.
What a heatmap does
On the platform the set is marked the moment each student finishes, so by Monday morning there's nothing to mark. What's there instead is a grid: students down the side, topics across the top, each cell coloured by how they went. Strong, ok, weak, not attempted.
You read it in ten seconds. A column that's mostly red is the topic the class missed, and that's the Tuesday lesson. A row that's mostly grey is a student who didn't do it, and that's a phone call. The tutor dashboard is built around this grid because it's the one thing a tutor needs before a class and the one thing paper can't give them in time. The heatmap entry in the glossary is the short version.
It goes a layer deeper when you need it to. Click a cell and you see the student's actual answers and how many hints they needed to get there. Click the ratios column and you see which questions the class got wrong most, with your worksheet beside them. So it's not just "ratios," it's "the two questions where the ratio had to be simplified first," and now Tuesday's lesson has a shape.
The tutors who aren't you
If you have casual tutors, the Monday morning problem is worse for them than for you. You've taught the Year 6 set for years and could probably guess what they got wrong. A university student in their second term with you can't, and shouldn't have to.
A heatmap gives every tutor the same Monday morning, whether they've been with you three years or three weeks. They walk into Tuesday knowing the topic and knowing the two names. It's the closest thing to consistency across a changing roster that doesn't involve you being in every room.
Why the set has to come back first
None of this works if the work doesn't get done. A heatmap of a class that didn't do the set is a grey rectangle. The homework that comes back guide is about the other half of the problem: making the six days between sessions produce something, so that Monday morning has something to show.
The two halves feed each other. Work that's marked instantly, with a worked solution the moment a student gets one wrong, is work students are more willing to finish, because they get something back for finishing it. Work that vanishes into a bag for a week is work that's easy to skip. So the marking isn't only how you get the Monday sentence. It's part of why there's a set to read on Monday at all.
This week
Make the tally sheet. Question numbers across the top, one row per student, a stroke for each wrong answer. Fill it in as you mark this week's set, and on Monday, before you plan Tuesday, read the columns. Find the topic. Find the names that have no strokes because they handed nothing in.
Then look at what it took to get that one sentence. If it took your Sunday, the instant marking page shows what it looks like when the set marks itself and the grid is already there.