While I understand that non-native speakers might shy away from writing reference letters in English (however, there's nothing stopping you from proof-reading their reference letter before they sign it), I don't understand why native and near-native English speakers don't want to write them. First of all, it's part of their job. I understand that they're busy, but as part of the management or admin team, they should fulfill their responsibilities. I also understand that they might not know you that well, especially if you're in a big school, however, they could still write a simple recommendation letter with your help.
What I've found is that people are being asked to write their own reference letters. This can be good and bad.
- You can write wonderful things about yourself (and some employers won't even read them before they sign).
- It'll have perfect English.
- It'll have all the info that you want it to have.
- You can write a bunch and personalise them for different employers and all your boss has to do is sign.
- Reference letters aren't worth much.
- If you have to write a lot of your own reference letters, they can look very similar.
- It's more work for you.
- You won't know what your boss really thinks about you.
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