Stumbling Block or Block Party: The Reality of an A/B Day Schedule

If you're a student, parent, or teacher in a block-schedule school (an A/B day schedule) you know the setup: four classes a day, about 90 minutes each, alternating days, for a total of eight courses. About a third of American high schools use some version of this system. It's been around since the mid-90s, it has vocal supporters, and the research on whether it works is... surprisingly thin.

I have some concerns. While I understand the goals, block scheduling is creating problems that nobody is naming clearly.

How We Got Here

Block scheduling didn't emerge from a breakthrough in learning science. It emerged from a set of practical pressures. Schools wanted to reduce the chaos of six or seven hallway transitions a day. Teachers wanted longer periods for labs, projects, and deeper class discussions. And proponents argued that fewer classes per day would feel less fragmented for students.

These are reasonable goals. But there was another force driving the shift that doesn't get talked about as much: states kept increasing the number of credits required for graduation. In Texas, students now need 26 credits to graduate. On a traditional six-period day over four years, that's only 24 course slots — not even enough to meet the state minimum. A block schedule, with its 32 slots over four years, doesn't just make room for the requirements. It makes them possible in the first place.

In other words, block scheduling was at least partly a logistics fix — a way to squeeze more courses into the same number of school hours. And somewhere along the way, the fix became the philosophy, as if more courses automatically means more learning. It also became a selling point. Schools, both public and private, market block scheduling as an innovative approach that gives students time for deeper projects, labs, and hands-on learning. That sounds great in a brochure. Whether it's happening in the classroom is another question.

What I've Seen (and What the Research Shows)

The 90-Minute Problem

The case for 90-minute periods rests largely on the idea that classes need extended time for labs, projects, and hands-on activities. But how often is that true? A science class might do a lab every week or two. Most other subjects (English, history, math) don’t often need 90 uninterrupted minutes.

So, here's what happens in a 90-minute block, over and over, at school after school: teachers either try to lecture for the full period — which is too long for anyone, let alone a teenager — or they teach for 30 minutes and give students the remaining hour for "independent work." In practice, that independent work time often means phones, Chromebooks, and socializing.

This isn't just my observation. Education researchers have identified these as the two most common failure modes of block scheduling. One teaching resource put it bluntly: lecturing for 90 minutes leads to behavior problems and poor retention, since student attention maxes out at around 15 minutes. And the teach-then-release model means students may only be getting direct instruction on half the material they'd cover in a traditional schedule.

One widely cited review claims block scheduling can work if teachers redesign their instruction for longer periods. But schools have been trying to do that for nearly three decades, and the results haven't materialized. That's not because teachers aren't trying. It's because for most subjects, there's no redesign that improves on shorter, daily contact with the material. You can rearrange a 90-minute lesson to make it less painful, but that doesn't make it more effective than 50 focused minutes every day. The format itself works against how students learn.

The Course Load Problem

We consider four to five courses per semester a full load for college students. But we're asking 15-year-olds to juggle eight different subjects, eight different teachers, and eight different sets of expectations and assignments. Yes, the block schedule spreads these across two days, so students only see four classes per day, but the total cognitive load of managing eight courses is still there.

Ironically, the original push toward block scheduling came partly from the recognition that students were overwhelmed by eight-period days. The solution kept the eight courses but hid them behind alternating days. The overwhelm didn't go away. It just got rearranged.

The Filler Problem

When you have eight course slots to fill, top students aiming at competitive colleges have no choice but to pack their schedule with AP and honors electives since colleges evaluate applicants based on the rigor of their coursework. The opportunity to take more classes sounds good on the surface, but it comes at the cost of less time on the fundamentals and burned-out students.

In some schools, activities like “office aide” and sports have become for-credit courses. And, to protect the GPAs of top athletes who also need strong transcripts, some schools have designated these as "honors" courses. When a school is giving honors credit for football practice, it's worth asking what "honors" means on anyone's transcript.

And there's a deeper question worth asking: Does taking more courses result in more learning? There's a strong case that students would learn more from focused engagement with fewer subjects. But the college admissions system rewards more — more courses, more APs — regardless of whether this leads to improved learning. Then, they complain that students are arriving at college unprepared.

The Spacing Problem

This one is backed by some of the strongest science in all of learning research. The spacing effect, the finding that we learn better when we revisit material at regular intervals rather than in large doses, has been replicated in hundreds of studies going back to the 1880s. Students retain more when they see material frequently in shorter sessions than when they get it in big chunks with gaps in between.

An A/B block schedule is, by design, the opposite of spaced practice. Students get a large dose of material on Monday, don't see that subject again until Wednesday, get another large dose, skip Thursday, and so on. For subjects like math and foreign language, where daily practice and continuity matter enormously, this is a real problem. The research on this isn't ambiguous. Daily contact with material, even in shorter sessions, produces better retention than every-other-day contact in longer sessions.

The Homework Problem

Block scheduling was supposed to give students more time to work during the school day, reducing the homework load. But when a significant portion of that in-class time is lost to attention and engagement problems, the work doesn't disappear. It follows students home. Not every student, of course, but we are asking a lot of teenagers in terms of self-discipline and focus. The students who struggle with this completely normal developmental reality end up with the worst of both worlds: unproductive time at school and a full evening of homework.

Making the Best of It

If you're in a block-schedule school as a student, a parent, or a teacher, you need a strategy to avoid the pitfalls.

Use the independent work time. Seriously. The students who benefit from block scheduling are the ones who treat that in-class work time as real work time. Every assignment finished during the school day is one less thing competing for mental space that evening. And teachers, when practical, can help by making assignments due at the end of the period rather than long-term work that's easy to put off. A deadline 45 minutes away focuses the mind in a way that "work on your project" doesn't.

Review on off days. The cognitive science is clear: even 10-15 minutes of review on the day you don't have a class makes a meaningful difference in retention. A quick review of notes, a few practice problems, a glance at vocabulary. It doesn't have to be a full-on study session — just a brief check-in with the material. This is especially important for math and foreign language. (Hint: this can be done if you have downtime during the school day.)

Stay organized. Organization is a superpower for all students, but it's a necessity on a block schedule. Keep a calendar and a to-do list with due dates (including interim due dates for long projects), along with meetings, practices, and everything else competing for your time. Start every day with a clear vision of what you plan to accomplish.

So, block party or stumbling block? Here's the real truth: if you don't party, you won't stumble.