How many villains are there at loose? I assume a lot. If lots of people have super powers, then lots of people will turn rotten, even more so than in RL because a super power would give them a feeling they won't get caught. Thus there's certainly a big market for heroes who are willing to fight villains, within reason (that is, fight battles they have a decent chance of winning), but who necessarily aren't heroes like in fiction who would without a second thought throw away their own life to save a stranger. They would just be like police officers with paranormal powers instead of a 9mm. Not all cops would jump between a bullet and a bystander or in front of a truck in a desperate attempt to push a civilian to safety.

If only utterly selfless, perfectly virtuous people would be accepted as heroes and the rest would be treated as lawless vigilantes, there would be very few heroes to keep an eye on villains who would be even more numerous.

What's going on in this show is pretty realistic in my opinion. Also keeping in mind there must be plenty of heroes who aren't really fit for combat. Hard to say how many would be attending this elite academy, though, especially considering that entrance exam.