How can they score 100% in exams? Is the system broken?

First things first: this isn't a comment on the intelligence or diligence of school toppers in the UAE and India. Allow me to concede that I am, quite literally, in awe of these teenagers who have scored 90, 95. even 100 per cent in their Class X and XII exams for the Indian curriculum. Hats off to them - and their schools, parents, tutors and siblings for playing whatever role they did in their achievement and success.
In my time (I passed out of a 10+2 Indian school curriculum system in 1991), a score of 75-per-cent-plus was actually considered 'distinction' and enough for one to make it through Delhi University's (DU) second cut-off list, if not the first. It's evidently a little different now. Yesterday, two students topped ISC Class 12 examination with 100 per cent marks. In 2015, the first cut-off list of two DU colleges for their BSc (Computer Science) undergraduate course touched the 100 per cent-mark. Which means that if the topper of my class of 1991 were to apply for an undergrad degree today, he won't stand a chance of being accepted, given his 'embarrassing' 90.4 per cent.
Getting a clean 100 per cent was always possible (admittedly not for yours truly) in objective subjects like Math or Physics even during my time, but it was near impossible to get anything more than 85 per cent in subjects which could be only graded subjectively - like languages. Today, 98 or 99 per cent in English is not unheard of. Is there a method in this madness? "The Indian school grading system is broken - it's leaking marks," the parent of a Class XII student back home told me recently. "Some of these streams just throw marks at students, making it a 'socialist' system of grading," she said with disdain. Even if she's exaggerating, there's definitely a case of grade inflation. Now add the fact that the growth in the number of higher education institutions of excellence in India hasn't kept pace with the number of toppers being churned out by its schools, and it does seem that the system is in need for some repair if not a complete overhauling.