Are
you serious?
There is no direct quote that says it is
halal to miss a fast during exams, there are several sources that cite missing a fast without a valid reason (Exams aren't one of them, i'm sure you think you're the centre of the earth and your exams are such a struggle but you're not and they're not), makes you worse than an adulterer. Missing a fast without a valid reason isn't just haram it's a
Major sin, you're playing with religion looking for loopholes even if there were a grey area why would you take the risk and lean towards the major sin???
No doubt these sources have already been provided to you as well but being jahiliyya you will lie to yourself and (even worse) other muslims that sitting still for 1-3 hours is turmoil enough to break a fast. If you're going to sin, then sin don't tell us about it and pray for forgiveness/make up the fasts, don't propagate lies to make yourself feel better about your actions.