Usually, no.
However, when you are applying for TEFL jobs, you can choose to apply for jobs teaching Young Learners, teens, or adults.
By the same token, you can apply to jobs which specify the level of the learners.
However, it is ultimately up to your employer to allocate which classes you will teach.
Of course, if you are an independent teacher you can choose to teach whoever you want.
Read more: 6 Differences Between Teaching Adults And Young Learners