Why does IELTS read [ˈaɪelts] when the I starts the word "International" so IELTS should read [jelts] instead.
Is it an exception?
IELTS is an hybrid abbreviation, part initialism (the "I"), and part acronym (the "ELTS" part). I is pronounced like "eye", then the E, L, T, S are pronounced as if there were a word "elts".
An initialism is an abbreviation consisting of initial letters pronounced separately (e.g. BBC).
An acronym is an abbreviation formed from the initial letters of other words > and pronounced as a word (e.g. ASCII ("asky") and NASA *"nassa").
I suspect the reason the "I" is pronounced as the letter is that there are very few English words starting with the letters "ie" and, if it were desired to treat the whole abbreviation as an acronym, the pronunciation would not be immediately clear, either to a native speaker or a learner, which would be a disadvantage given the context. I can imagine it would work in Welsh, though. There is a Welsh boy's name Ieuan, pronounced "yoo-an".
Other abbreviations starting with "I" include ICANN (eye-can) which is pronounced in that way, and IBAN (ee-ban), which is not.