Block Lessons: What They Are and How to Place Them

Five hours of maths a week. The teacher wants double periods, because single ones are too short to get into a topic. The lab lesson needs three periods in a row so an experiment doesn't stop halfway. Both are perfectly reasonable requests. Put into a timetable, both make everything harder.

What is a block lesson?

A block lesson is a subject taught for two or three periods in a row on the same day. A five-hour subject split 2+2+1 becomes two blocks and one single period a week. A block sits on consecutive lesson periods of the same day. It never crosses into another day, and if your bell schedule has a separate break (lunch, for example) between two periods, it doesn't cross that either.

Block patterns in Atlas

For each lesson requirement in Atlas you choose how the weekly hours are split:

A session is at least 1 and at most 3 periods long. Atlas does not build blocks longer than three periods.

The consecutive-period guarantee

In Atlas a two-period block always lands on two consecutive periods of the same day. It is never split across days, and no other lesson comes between.

The rule holds for hand edits too. Drop a block where there aren't enough consecutive periods and Atlas refuses the change and says why: “This block lesson doesn't fit the chosen slot (not enough consecutive periods).”

Why block lessons jam a timetable

A single-period lesson can go into any free period of the week. A three-period block needs three free periods in a row on the same day, for the teacher, the class and, if needed, the room, all at once. A teacher's closed periods, a fixed lesson or a full lab can easily close that three-period window.

Atlas usually sees this before building, in the pre-check. You get one of these headings:

• “The block doesn't fit in any day”: the block is longer than the school's longest day.
• “No consecutive window for the block”: there is no run of open consecutive periods left for it.

And when a timetable is tried and can't be built, one of the fixes Atlas tries is changing the lesson's block pattern. It shows that suggestion only after trying it on the whole timetable; see what to do when the timetable won't build.

Other rules that go with blocks

• All hours of a lesson on one day: every weekly hour of the lesson on the same weekday. A required rule.
• Keep a lesson together, not scattered: a preference against leaving too few hours on a day.
• Not on the same day: two lessons on different days, for example two heavy blocks.
• Don't put heavy subjects back-to-back: the subjects you mark as heavy don't run in a row.

Practical advice

1. Don't make every subject a block. Choose the ones that truly need two or three periods.
2. Check the closed periods of the teacher who wants blocks. If closed periods cut the day, the block won't fit.
3. For blocks that need a lab or a workshop, count the rooms. How many rooms the category has decides how many such blocks can run at once.
4. Run the pre-check first; most block problems show up there.

How blocks are built together with the rest of the timetable is in the step-by-step guide.