While sex discrimination legislation is hugely important, it muddies the waters when people cry 'discrimination' in cases where it is not clear cut and where it's doubtful there's any case to answer.
A few points:
ALL people, on becoming parents, have caring responsibilities. How they choose to manage these is to a large extent personal choice. While a woman is on ML she is still employed with full employment rights. After that she can return to her job, and the two parents can outsource some of those caring responsibilities. Or she can resign. Or the father can resign to become primary carer.
In the ops case she has had 5 years out of work. As a teacher of some years experience, we can assume she was earning, say 30k. Not big bucks but not a pittance. Enough for childcare if she had chosen to keep her job. We can also assume her husband/partner earns at least as much as her, otherwise it would be very odd for the person on the lower income to keep working while the professional on 30k gave up!
In other words, this was a CHOICE.
I'll also point out, again, that the majority of English teachers are female. Op is most likely losing out against OTHER women, who have chosen to keep their skills up to date. It is very very hard to get into English teaching right now. If there are other people out there who have equivalent qualifications and more recent relevant experience then frankly they are getting the jobs on merit. Why should they be discriminated against if they are the better candidate.
And this is absolutely not a 'veiled attack on SAHM' as some one ludicrously suggested- its just plain common sense.