The teacher recognised, the longer she was in her job, the more exasperated and impatient she had become the childern under her care. This anguish was present from the earliest hours of the morning. But knowing the children were not purposefully behaving badly, not being malicious in their actions, but acting through instinct-- like animals-- this helped her to face her emotions in order to face them each day.

(I think).

Thanks David, this is also what I understand (on a very personal level, as I used to teach and experienced that very anguish first hand). Now the problem is, how do you translate the sentence in bold?...

It [the phrase] imposed itself, like a sort of excuse, or indulgence granted [to the sinners] in advance...?

I think the sentence you're struggling with refers to the Roman Catholic theology of indulgence.
http://en.wikipedia.org/wiki/Indulgences

"The Idea possessed me: 'The children are more like animals than human beings.' As time passed, I became more distressed and less able to face the students... but The Idea gave me strength and helped me to go on. It was the crutch I leaned on; pre-forgiveness for whatever sins I might commit in the classroom that day. It gave me the strength to go on. To face them."

That's really interesting Sandy, Jonathan on the French side of this blog agrees with you. I really hadn't thought of this reading of "indulgence" and I suppose that the general context of the play would be able to tell us whether it should be taken in a religious sense or not.

My rendering of the bolded text, respecting the same structure as the French version, would be something like:

The sentence served as a sort of excuse, a pretext for being indulgent,

Although I see the similarities with the RC thinking, my understanding is that the teacher is being indulgent towards the pupils.

But it's not easy - I would be interested tosee what you finally go with

Goodness Andreas, I hadn't thought about that either. To me, the indulgence was directed at the teacher, who needn't be too hard on himself because the pupils are such a nightmare, so he shouldn't feel bad about having such a difficult time teaching them. The plot thickens...

To me the teacher is becoming more and more anxious about teaching the pupils, and to ease his conscience, he has convinced himself that whatever he does is of no use because the pupils are acting purely on an emotional level

There is no mention that the children are behaving badly or that the teacher is doing a bad job. To me, this paragraph describes the teacher's psychological mechanisms.

Or have I got hold of the wrong end of the stick?

I too totally took it to mean indulgence in the catholic sense, because of the word prealable (as usually you seek an indulgence afterwards) and I thought the indulgence was for the kids, not the teacher, that she continually tries to excuse them and forgive them in advance ('they know not what they do'), so that she won't feel so bad about what's happening

I agree with the others; the allusion to Catholic indulgence is apt, particularly in the sense of a ritual of absolution. So I'll offer only a quick translation:

It became a ritual (pre-requisite), a sort of absolution, a pre-emptive (or prior) forgiveness (or leniency), like a stimulant, a drug, a cure to be swallowed each morning. To be able to face them.

I'm THE Jenny translating the play and having problems with this particular sentence. Thank you very much for all your comments. The Catholic reading of it is very interesting; but the suggestion that the teacher tries to convince herself that the children aren't really bad doesn't fit because the play tells the story of the teacher driven so insane by her pupils that she shoots them! I think my next move will be to email the playwright and see how he responds to this suggestion. Any ideas are welcome! Thanks again.

Hi Jenny
Do let us know what the playwright says, won't you? And if the play gets staged in English? Very best wishes with your translation.

A bit late I know, but here's my pound of flesh. I thought that the indulgence was more like the teacher giving in to a sort of craving, and felt that self-indulgence may be closer.

This phrase kept popping uninvited into my head: "Pupils are like animals: they don't act through intelligence but through instinct." Year by year, the fear struck earlier each day. Before I opened my eyes, as the alarm clock went off, the sentence became part of me, fed by my thoughts and viscera. It forced itself on me as a kind of excuse, a necessary bit of self-indulgence, like a stimulant, a drug, a pill that you swallow each morning. To face Them.

The extract is a bit short but maybe the following would work:

Elle s'imposait, en une sorte d'excuse, d'indulgence préalable, comme un stimulant, une drogue, un remède qu'on avale chaque matin. Pour les affronter

I couldn't get this idea out of my mind. It was my excuse, my forgiveness for what I was about to do. It was like a stimulant, a drug, a pill I had to swallow every morning. I needed it to face them.