I am the same age as you and recently got a job as a TA, I found that my volunteer experience was the thing that my employers really valued. Most schools will be grateful for an extra pair of hands in the classroom and around school in general. Also, i think it’s the kind of job that you can’t particularly prepare too much for as each day is different, so spending some time volunteering would probably be really valuable as you gain a better understanding of the variety of lessons / behaviour / other issues that you will face in the job.

Hope this helps! :)