Yes it does happen KW, If you turn out to be useless and a pain in the rectal orafice they have the option to get rid of you . I imagine it is to do with them investing a fair amount of money on your training and college work before reaping the benefit when you are skilled and earning them their fortunes.
At 21 you may decide to sod off to their competitors or become self employed.
So , as I'm sure you realise, you need to make those three months count.
As regards college , I and many others did day release ,which was one day a week at college ,four on site . If block release is an option then take it , as with day release you tend to have forgotten half the stuff by next week. Well I did anyway.
The JIB will register you as an apprentii and issue a grade card ( apprentice) . When you attain whatever the quallies are these days they will upgrade you to Electrician Grade. They used to monitor your training too, I presume they still do, you may have to submit a skills report to them as you go along .
You can have a look at their website online , which shows the rates of pay for employed apprentices and sparks . You may be on a lower rate for those 3 months, put up with it , one day you will be a millionaire , Rodders, like the rest of us on here.
:coat
Although I am self employed, I still keep my JIB card renewed (I have to pay for it) as it is the only thing I have that says I served an apprenticship ( The company having dissapeared years ago ) but JIB still hold your records.
As said before , stay with the Forum and let us know how you're getting on.
Deke