How do I phrase this covering letter?

[TitusAndromedon]

I am a secondary teacher currently on maternity leave. I requested to go back part time, but was turned down. Fortuitously, a part time job in my subject has come up at another local school, so I'm applying and rather desperate to be successful! However, I'm struggling to explain in my letter why I want the job. It is a step down because I will lose my TLR. I've only ever written letters that outline my ambition and desire for progression. Is it okay to say that I'm attracted to the job because it is part time, or should I try to come up with some other reasons? How can I phrase it?

I would tell them all the fabulous things you have to offer just like any other job. I was always told to make applications about what you can offer them, not why the job would be good for you.

If your work history shows that you are returning from maternity leave, I'd say it's pretty obvious why you want to be part time.

Life work balance is a good phrase. Big up the school and why you would want to work there as well.

Exciting new challenges that come with a new role.... Home/work balance but part time will allow you to continue to be as dedicated to the position as you were before maternity....