Specific responsibilities can vary from one client to another.
When applying for this type of job, a cover letter enables you to articulate why you are interested in the position and lets you highlight the unique skills and characteristics you bring to the role.
Present in all formal applications will be a job description and person specification.
These should be read carefully: skills, experience and characteristics should match the requirements and this will be apparent in a good cover letter.
Hobbies and previous jobs, if they illustrate organisational skills, flexibility or creativity, can also be successfully worked into a great cover letter for a classroom assistant position.
A person who enjoys painting or scrap booking, for example, could put those skills to use in making classroom displays, while referring to a previous job as a secretary or a receptionist can illustrate the ability to work under pressure or diffuse difficult situations.
Informal experience with children, as well as experience that doesn't involve children at all, is also relevant to an application if worked into a cover letter correctly.
Experience with younger siblings or one's own children displays experience and fondness for kids; including a few examples of structured activities the writer has organised and been responsible for helps, too.
Finally, always remember to be truthful when writing a cover letter, as this quality is possibly the most important of all for anyone working in a classroom environment.
Ask a friend to read through the application before sending it, and don't be afraid to ask for an honest opinion.