Unfortunately, headteachers are not qualified SLTs (Speech & Language Therapists).
Although it is true that SOME language delays are due to Adult Child Interaction - it is most definitely not your 'fault' if you are advised these techniques either, often it is just you hadn't had them modelled to you previously e.g seeing other parents strategies, own parents may not have used them, or have tried everything to the point that you did too much - which is often the case!
e.g. yes a child who is not spoken to and is left alone has more likelihood of lang delay as is one plonked in front of tv 24/7.
ACI strategies can include things like reducing your talking - a lot of parents try to over compensate for child lack of speech and talk for them, e.g. "Oh look Johnny, look at the train, it's a lovely train isn't it johnny lets play with the train johnny" or they interrogate "Whats that?! whats this?" or they demand manners 'Thankyou' (well it's not called a thank you and manners are a later age concern - not early language - if they give you a car, you say Car if they are not using the words)
another thing that happens is parents care too much in the sense of they anticipate needs and don't give the child the option to ask.
"Here's your milk johnny."
Had you held up the squash bottle and the milk bottle - chances are johnny might point to what he wants (milk) then you could say "Milk" as he points - then you have to be a little bit mean "Milk?" and wait for them to try to say it, do it over and over and over - Johnny will learn that by saying milk he will get milk - if he has been going 'uuurgghghhh' and pointing and you let him have the milk, he is being taught - by a parent / caregiver - and having it reinforced that 'uuurghhghghgh' is the word for milk.
additionally older siblings will also anticipate younger siblings needs or SPEAK FOR THEM.... Johnny goes Ug ug - Mary goes "Here's your ug ug" and hands him his milk
another thing that causes speech difficulties to start with is when they start attempting to speak whilst using dummies and bottles - the worst thing for speech (kids produce a slushy sound like they've still got a bottle / dummy in when they talk) and thats because their tongue is used to being further back and again is a learned behaviour - by all means bottles and dummies in bed with no talking to soothe - if talking, get them out of their mouths or you will be in a world of trouble later on. THIS CAN ALSO HAPPEN WITH THUMB AND FINGER SUCKING - so remind them to take their fingers / thumb out of mouth if going to talk e.g. "I can't hear you with your fingers in your mouth Johnny" wait until takes out "Ah much better!!! you want milk?! great! let's get some milk!" rewarding the positive speaking behaviour, and refusing to cooperate with the bad behaviour.
kids with other issues are a different board game - so it's a delay until 5 yrs old - after that it is more likely to be a language disorder or some other kind of thing directly affecting language - SLI (now DLD) is a particular language learning disorder, auditory processing difficulty - difficulty decoding language as it goes in, attention difficulties - if you can't sit still and listen, you are not going to be hearing the language to learn it and use it, deafness / glue ear etc again if you can't hear it properly you will say it wrong, learning disability / autism etc - might not want to engage in social interaction such as playing.
and play is the best way to encourage language. some toy vegetables etc and you COMMENT "Johnny you have the apple," and when they start saying 'apple' they will hand it to you "ooh apple!" then johnny says "apple" "yes! it's an APPLE!" once they have one word level (apple, dog, mum, milk etc) then you EXPAND : Johnny hands mummy apple says apple (you're following their lead always) "yes! Red apple!!!" they then are hearing 2 words 'red apple' 'tasty apple' crunchy apple' (sound effects crunch crunch etc always good - this is the stage kids start getting nursery rhymes - if they can't sit and listen and share joint attention e.g. both looking at apple and kid showing you apple - they ARE NOT GOING TO FOLLOW RHYMES ETC...
heres a pyramid as a guide - the bottom layers must be there or the top won't come - this is what SLT does - www.chatterslt.co.uk/?p=2621
if they can't play / don't socially interact / understand cause and effect (you know your kid is tossing a spoon off his high chair, you pick it up they giggle, and repeat until crazy = cause and effect) THEN THEY WILL NOT GET WHY THEY NEED TO SIT AND LISTEN AND WATCH
if there is no attention / too short attention then they won't be able to take in language
if you can't take in language you can't understand it
if you can't understand it you can't attach meaning
if you can't attach meaning you can't use language
hence no speaking in young children if any of the above are missing - and that is the level you are working on.
you need your kid to follow your pointing / you follow theirs e.g. look a dog!!!! (point) if they don't look and they are around 1 you need to check hearing / see paediatrician for referral -
we expect one word / pointing / indicating wants and needs at 1 yrs; 2 words "Mummy come!" "Daddy up!" at 2 (some kids are more advanced than this, others might be a bit behind)
but if a 4 yr old is not saying sentences e.g. Mummy go shopping, Look at teddy, Daddy jumping! with actions, then ask gp / paediatrician to refer to SLT.
really hope this helps you all - message away with any queries.
bottom line, for some children it is a lack of interaction, but for many there are lots of other factors involved, but try not to worry there's lots to help them communicate to the best of their ability! 