Test - Teach - Test (TTT) is a lesson format which is useful when you know or suspect that learners have some knowledge of an area but are unsure how much. It allows you to find out, and then base your teaching in the rest of the lesson on the results.
The sequence starts with an initial Test stage. This could be literally a test - eg if you wanted to check whether your learners could control various exponents used to make polite requests, you could give them a multiple choice test with items such as :
3. It's very hot in here. Would you mind ....... the window.
a. to open. b. opening c. open d. if you open e. that I open
However, all this really tells you is whether they understand and recognise the form of the item - not whether they would actually use it appropriately. So an alternative would be eg to give them five situations to roleplay in pairs, including :
3. You're in the office and it's really hot. Ask your colleague to open the window.
As you monitor the pairwork you can then make notes on ...
a. The exponents the learners are using spontaneously and accurately
b. The exponents they are trying to use but are using inaccurately
c. Those that they are avoiding altogether.
This will then allow you to decide what to focus on in the Teach section. For example, if you've heard that all the learners are using *Can you to open the window you might then board and focus on it, correcting it and drilling it. On the other hand, if you heard this mistake from only one learner, while the rest were using it correctly but continuously, then you might board it, focus on and correct it for the benefit of the learner that had the problem (we'll call him Davide) but then , for the benefit of they others ask if they could think of an alternative word that could replace Can - and elicit or feed in Could /Will / Would - just one of these or more, depending on how much you think the learners can cope with (based on eg whether the words and their use are already known to them or are new). The lesson then proceeds with drilling and further practice of these new exponents.
In a third scenario, it might be that the learners are using Can/ Could / Will / Would accurately and in alternation, but nothing else. Now you know they're ready for a greater challenge and can introduce Do you think you could... or Would you mind + Ving - and the lesson proceeds with practice of these exponents.
This format also helps you differentiate between the learners. Davide was still having problems with Can you... - so you correct and explain it for him, and then tell him that for the rest of the lesson you want to hear him using it. Ingrid was using Can and Could accurately but avoiding Will and Would, so you focus on these for her and tell her to practise them in the activities to come. Belem on the other hand was using all the modals accurately - so you introduced Do you think you could... and told her that for the rest of the lesson she should go on practising that. And so on. Your follow up activities may be gapfills, roleplays or other activities where the learners can use "their own" exponent, thus each working at their own level.
The final Test stage could be a repeat of the original activity or a different one, but its aim will be to see whether the learners have improved their performance either in the sense of using the language more accurately or with a greater range of structural exponents, vocabulary or whatever the aim of the Teach stage turned out to be.
Woodward, T. Planning Lessons and Courses, Cambridge