October 26, 2026 · 3 min read
How to Spread a Subject's Weekly Hours Across the Days
Three hours of maths on Monday, none on Thursday. Correct on paper, tiring in class. Here is how to spread a subject across the week, and which rules push against each other.
At a parents' evening someone asks: “My child has three hours of maths on Monday and none on Thursday. Why?” The timetable follows the rules: no teacher clash, no class clash. But the spread is poor. A timetable without clashes is not enough; how the hours are spread across the week matters too.
First, the pattern
The first step of spreading is how a subject's hours are split. A five-hour subject can be Single (1+1+1+1+1), Double (2+2+1), Mixed (3+2) or a Custom pattern of your own. The pattern decides how many days are needed: 2+2+1 needs at least three days, five singles need five.
The rules that steer the spread
| Rule (its name in Atlas) | What it does | Kind |
|---|---|---|
| Spread a lesson evenly across the week | Shares the subject's hours evenly between days. | Preference |
| Spread a lesson across enough days | Spreads the subject over as many different days as possible. | Preference |
| Keep a lesson together, not scattered | Avoids leaving too few hours on a day. | Preference |
| Cap a class's lessons per day | Puts an upper limit on a class's lessons in a day. | Required |
| Not on the same day | Keeps the lessons you choose on different days. | Required |
Heavy subjects: in the morning, but not all on one day
Most schools want subjects like maths and physics early in the day. Atlas has three rules for that, and you decide which subjects count as “heavy”:
- Schedule heavy subjects earlier in the day: pulls heavy subjects before a period you choose.
- Don't pile heavy subjects on one day: limits a class's heavy subjects per day.
- Don't put heavy subjects back-to-back: keeps heavy subjects from running in a row.
If two particular subjects shouldn't sit side by side, say a test lesson straight after PE, there is Don't put two subjects back-to-back. To stop a class going too long without a break, use Avoid long back-to-back lessons for a class.
The rules pull against each other
Some spread rules pull in opposite directions. “Spread a lesson across enough days” wants the subject on five days; “Keep a lesson together, not scattered” doesn't want a lone single hour on a day. Both can't be fully met for the same subject at once.
When you prioritise preferences, ask yourself: for this subject, what matters more, seeing it every day or going deep in one session? Make that one High and the other Low.
Required rules never bend. If the class's daily cap and rules like Not on the same day are set too tight, the timetable may not build. Atlas then shows which rules block it together: What to do when the timetable won't build.
How to check the result
Two reports help once the timetable is built. Class Density shows each class's load by day, and Preference Satisfaction shows which preferences were met and which strayed furthest from their target. If you don't like a spread, move the lesson by hand, or change a rule's priority and build again.
A short roadmap
- Choose the pattern for each subject first.
- Set a realistic daily cap for classes.
- Mark the heavy subjects and add the morning rule.
- Give the even-spread or wide-spread preferences a priority.
- Build, then read the Class Density and Preference Satisfaction reports.
How blocks affect the spread is in block lessons; the whole timetable is in the step-by-step guide.
Frequently asked
Can a subject's hours be spread evenly across the days?
Yes. The “Spread a lesson evenly across the week” rule tries to share the subject's hours evenly between days. It is a preference, so you can give it a priority.
How do I get heavy subjects into the morning?
Add “Schedule heavy subjects earlier in the day”, choose the heavy subjects and the cut-off period. Atlas tries to place those subjects before that period.
Can I limit how many lessons a class has in a day?
Yes. “Cap a class's lessons per day” is a required rule; Atlas never goes over it.