Praise be to Allah.
For a man to use the word of divorce (talaaq) lightly is a grave mistake, which may lead to the disintegration of his family when he does not want that. Allaah has not prescribed divorce to be something that is taken lightly or spoken carelessly, or to play with women’s feelings, rather He has prescribed it for the man to use it when he wants to end a marriage if there is a reason to do so.
What the man must do is guard his tongue and restrain himself from using the word of divorce in matters where divorce is not warranted, so that he will not regret it when it is too late for regret.
Divorce at times of anger may or may not count as such. This has been discussed in the answer to question no. 45174.
To sum up, in the event of anger in which a person is out of his right mind, divorce does not count as such, as is also the case with anger in which a man is not in control of himself because an argument or fight has gone on too long.
The man is the one who can recognize the degree of anger that he reached, and can decide whether divorce counts as such or not.
Issuing a threefold divorce in one go, such as saying “You are thrice divorced” or “I will divorce you three times” counts as a single divorce according to the view favoured by a number of scholars.
If your anger did not reach the degree that your divorce did not count, then you have issued one divorce in this case – if your wife went to school – and you may take her back so long as her ‘iddah has not yet ended.
See the answer to question no. 36580 for more information.
And Allaah knows best.