Children are kinaesthetic learners.
Experiencing something physically will embed in them, all the way to cell level. So, using signs for colours, numbers, names of people and questions, allows children to experience learning at a much deeper level. Older children (7+) can especially benefit from using sign language to help with spellings; again, the physicality of spelling words on your fingers provides a deeper understanding and knowledge.

Children process visual information quicker than aural words.
Their brains can de-code information via the eye more easily than via their ears. Children don’t tend to have ear dominance until 2 or 3 years of age so will hear, and process all information they hear, twice –  once for each ear.   Using the signs for ‘stop’ or ‘danger’ will get a quicker result than just shouting very loudly.   The technical phrase would be that it helps support receptive language skills.

This is even more evident in children with SEN or additional needs.

Signing can be used as a respectful form of communication.
Signing allows a child to ask to go to the toilet without announcing it to their class or a room full of strangers. It gives less confident children a simple way of asking for help or sharing information.

Signing can be used for emphasis or expression.
An excited two year old may be able to tell you they can see a boat or a hippo but by also signing, they are adding expression and intonation to their speech. The physical emphasis can also provide better understanding for the person on the receiving end of the information.
From a parenting point of view, signing is an invaluable tool when out and about. Using signs for ‘stop’, ‘danger’, ‘wait’, ‘please’, ‘thank you’ (and many others) provides a way to communicate without drawing attention to the child or the behaviour.

Signing is great for improving or advancing motor skills.
Good dexterity opens up a whole new world to little ones, allowing them to safely handle small and unusual objects. Signing brings an awareness of the hands and fingers and how they can be moved and manipulated into different shapes. Studies show that even 4 and 5 year olds will have difficulty with their fine motor skills and signing can help to develop this.

Signing adds an extra layer of learning.
Not only are children learning another language (BSL is classed as a Modern Foreign Language) but their brain is boosted by the added information the kinaesthetic experience of signing is giving them.  As Marilyn Daniels states in her book Dancing With Words, signing is quite literally ‘language in motion’ and therefore helps children to learn more ably.

It can be an invaluable tool for children whose speech may be considered delayed – slightly or more severely. 
Not all children conform to the ‘norm’ and may take a little longer to get some of their speech sounds perfected. Sign language bridges that gap, helps support emerging language structure and reduces frustration which often leads to meltdown.

Most of all IT’S FUN!
All children (and many grown ups!) love action songs and rhymes – from ‘Old MacDonald’ to ‘Kentucky Fried Chicken’.  Using sign language formalises this natural enthusiasm and instinct to something that can aid understanding, communication and education for a lifetime.