How Long Should an Intervention Last in the Classroom?

Most classroom interventions run 15 to 30 minutes a session, three to five times a week, for a cycle of six to twelve weeks before you judge them. Primary sessions sit at the short end, secondary at the long end. The total dose matters more than any single number, and the date you review it matters more than either.

This is for class teachers, teaching assistants and SENCOs deciding how to timetable support and when to stop it. There is no official figure to quote. What follows are the ranges schools actually work to, and the things that push a particular intervention towards the top or the bottom of them.

How long should an intervention last in the classroom?

An intervention lasts as long as it takes to close the specific gap it was set up to close, which in practice means a fixed cycle with a review at the end and a decision to stop, continue or change. Six to twelve weeks is the usual cycle. Anything running with no end date is not an intervention, it is provision, and it should be described that way in the pupil’s plan.

Three numbers define the dose, and you have to set all three:

• Minutes per session. How long the pupil is actually working, not how long the slot is.
• Sessions per week. Usually the number that matters most.
• Weeks in the cycle. Fixed at the start, with a review date in the diary.

Four things move those numbers:

1. The size of the gap. A pupil six months behind on number bonds needs a different dose from one who has never decoded a word reliably.
2. Age and attention. Reception and Key Stage 1 pupils get short and frequent. Key Stage 3 and 4 pupils can hold a longer session, and often need one because the content is harder to break up.
3. Group size. One to one goes faster per minute than one to six. A group of six is a small class, and it needs the same planning a class needs.
4. The timetable. In most schools this is the honest answer. A 20 minute slot exists between assembly and maths, so the intervention is 20 minutes long. That is not a scandal, but be clear that the slot chose the dose rather than the assessment choosing it, because that changes what you can fairly expect at review.

The SEND Code of Practice describes support as a four part cycle of assess, plan, do, review. The duration question is really a question about how long the “do” part runs before you are honest about the “review” part. Schools that still talk in waves of provision are describing the same idea: whole class teaching first, then targeted small group, then something more intensive and individual.

How long should an intervention session last?

Fifteen to twenty minutes is right for most primary interventions and twenty to forty for secondary, with the test being whether the pupil is working for nearly all of it. A session that is too long produces compliance rather than learning, and the pupil learns to survive the twenty minutes instead of doing the twenty minutes.

Intervention	Typical session	Usual frequency
Phonics catch-up (KS1)	10 to 15 minutes	Daily
Reading fluency or paired reading (KS2)	15 to 20 minutes	3 to 5 times a week
Number fact fluency (KS1 to KS2)	10 to 15 minutes	4 to 5 times a week
Pre-teaching vocabulary (any phase)	10 to 15 minutes	Once or twice per new unit
Small group literacy or numeracy (KS3)	30 to 40 minutes	2 to 3 times a week
Speech and language programme	10 to 20 minutes	As directed, often daily
Behaviour or SEMH check-in	5 to 10 minutes	Start and end of each day

Two practical corrections to those figures.

First, count the walk. A 20 minute slot that includes fetching a pupil from class, settling them and walking them back is a 12 minute session. If the slot is the constraint, shorten the activity rather than letting the activity be cut off at the end, which is where the review and consolidation live.

Second, frequency generally beats length. Splitting an hour a week into four fifteen minute sessions gives four chances at retrieval instead of one. If you have to choose between a longer session and a more frequent one, take the frequency for anything that is fundamentally about recall: phonics, number facts, spelling, key vocabulary.

How many weeks should an intervention last?

Six to twelve weeks, with a checkpoint at the halfway mark, is the range almost every school lands on. It is not arbitrary. It maps onto the half term, so it fits the way the year is already broken up, and it is long enough for a genuine change to show without being long enough for a failing intervention to eat a term.

Set the review date on the same day you set the start date. If the start is the first Monday back and the cycle is eight weeks, the review is already in the diary before the first session runs.

At the halfway point you are looking for direction of travel, not a result. Nothing moving at all after three or four weeks is information: usually the target was too broad, the pupil was absent more than the record suggests, or the programme is pitched at the wrong level.

Interventions rarely get formally stopped. They fade, generally in the week the teaching assistant is covering a class, and nobody notices until someone asks in July what happened to it. A dated review is the only thing that reliably prevents that.

Writing the intervention target in the same way you would write any learning objective, with a condition and an observable behaviour, makes the review much faster. “Reads 40 words per minute on unseen Year 3 text” can be checked in two minutes. “More confident with reading” cannot be checked at all.

What are 5 examples of interventions?

These five cover most of what runs in a typical primary or secondary school, and each shows how the dose follows the gap.

1. Daily phonics catch-up (Year 1 to Year 2). Ten to fifteen minutes, every morning, one to one or in a pair, targeting the specific graphemes a pupil missed rather than restarting the programme. Run for a half term, then re-check against the same set of sounds.
2. Repeated or paired reading for fluency (Key Stage 2). Fifteen to twenty minutes, three to five times a week, with the pupil re-reading a short passage until it is fluent before moving on. Measure words per minute and errors on an unseen passage at the start and end of the cycle.
3. Number fact fluency, often run as precision teaching (Key Stage 1 to 2). Ten minutes daily on one narrow target, such as number bonds to 20 or the six times table, with a timed probe at the end of each session that produces a data point without any extra recording.
4. Pre-teaching vocabulary before a new unit (any phase). Ten to fifteen minutes, once or twice before the unit starts, teaching the six or eight words the unit depends on. This is the cheapest intervention in the building and the one most often skipped, because it needs the class teacher to look a fortnight ahead. It fits naturally into the way a scheme of work is sequenced.
5. Check-in check-out for behaviour and engagement (Key Stage 2 to 4). Five to ten minutes with the same adult at the start and end of every day, against two or three specific targets on a card the pupil carries. Runs for six to eight weeks, then reduces deliberately rather than stopping dead.

None of these is a menu item to pick from. The assessment decides which one, and the size of the gap decides the dose. Choosing the intervention first and then working out what it might fix is the most common way a term of teaching assistant time gets spent on nothing in particular.

When do you stop, extend or change an intervention?

At the review there are three honest outcomes, and picking one is the whole point of having a review.

• Gap closed. Stop, and put a date in for a light check in four to six weeks. Pupils who close a gap in a small group sometimes reopen it back in a class of thirty, and you want to know that in November rather than in May.
• Progress, but not closed. Run one more cycle with the same method, and say at the outset that this is the second and last cycle before something changes.
• No real progress. Change the method or reassess the need. Do not repeat the same cycle louder. Running a second identical cycle because nobody wanted to call the first one a failure is a common way to lose a term of teaching assistant hours.

The decision falls apart when the exit criteria were never agreed at the start. The class teacher remembers the aim as “better with blends”, the teaching assistant remembers “more confident”, and the meeting ends with everyone agreeing to keep going because nobody can say what stopping would look like. If those two lines never get written down, Projan is one of the tools that will prompt for them, running the planning exchange as a set of questions in Microsoft Teams, asking what the pupil should be able to do by the review date and who is checking, then writing the answers out as dated actions.

Keep the record small enough to survive the term: one measure taken the same way at start, midpoint and end, a tick for attendance, and one line a week from whoever delivers the sessions. That is enough to make a fifteen minute review meeting produce a real decision.

Frequently asked questions

What is an example of an intervention? A Year 1 pupil who failed the phonics screening check gets ten minutes of one to one phonics every morning before the whole class lesson, working on the specific sounds the check flagged, for one half term. That is a complete example: named gap, named pupil, fixed dose, fixed end date, and a re-check that decides what happens next.

Who should deliver classroom interventions, the teacher or a teaching assistant? Usually a trained teaching assistant delivers, and the class teacher stays accountable for the plan and the outcome. That split only works if the TA has the programme, the target and the recording sheet before session one. Handing over a vague instruction to do some extra reading is how an intervention turns into supervised time.

Should interventions be delivered in class or by withdrawal? In class where the pupil can still access the lesson, by withdrawal where the task needs quiet, repetition or a different starting point. Withdrawal costs the pupil whatever they miss, so check what that is before you fix the slot. Pulling a child out of the same subject twice a week for a term creates a second gap while closing the first.

Can an intervention run for a whole academic year? Support can run all year, but call it what it is. A year long arrangement with no review points is provision, not an intervention, and it should sit in the pupil’s SEN support plan with its own targets. If you genuinely need a year, break it into termly cycles so there are three moments where continuing is an actual decision.

How much progress data do you need to collect? One measure, taken the same way, at the start, the midpoint and the end. Attendance for each session, marked as a tick. One line of comment a week, written by the person delivering. Anything more gets abandoned by week three, and a half finished record is worse at review time than a small complete one.

Pick the dose from the gap, write the exit criteria before session one, and put the review date in the diary at the same time as the start date. An intervention that runs for six weeks and ends in a decision is worth more than one that runs all year and ends in a shrug.