CS teacher tip of the day:

server side input checks and sanitization are always useless. because nowdays all browsers have javascript enabled by default and nobody disables it. so client-side checks are safe.

me: ***WTF!?!***

CLIENT "So my nephew who does stuff with computers built it and we are ok with how it all works so don't worry about changing that. "

DEV "so like you have a public form with no input filtering, spam mitigation let alone sanitization or remote concern for security. Basically you have a Json flat file that is 34mbs of links to, viagra, replica watches, nock off name brands and one real estate company. It is getting about 15 submissions an hour. Since you don't want me changing how it works are you happy to just leave all that ?"

CLIENT "no no we don't want all that but we have no route to delete it, can you just stop all the spam and let us continue on?"

DEV "ok so back to my first question can we rebuild all of this properly, or do you really want to just leave it all"

:/ FML

If you have any project (personal or not, doesn't matter) that does not have proper code comments and documentation and you don't want to make one because of the effort (maybe even "wasted" effort), think again. When commenting on a wall of code to say what it does, you may find a better way of doing what you have to do, possibly increasing performance, or improving security.

I have been able to do better input sanitization for a method on a personal project of mine because of this.
Don't use the amount of effort for proper documentation as an excuse not to make one.

Teach things properly, most teachers are confused and they start throwing keywords at even more confused students who then have no clue what they are doing and they then ask me to do their work for them showing me their unindented(well... kinda, they all seem to fight with the IDE, which is trying to properly indent their mess, for some reason), teachers think that Turbo Pascal is the way of life and that it is used everywhere(one teacher tried to tell me that Pascal is used in the stock market and in modern operating systems - U wot m8?! how high are you right now) and they don't teach user input sanitization and type checking, they stare at you like you are the fucking satan when you dare to use objects, collections and abstraction because they are scared to death of that stuff... and then they think 60 minutes is enough to teach HTML, CSS, JS and PHP in one go(which they even don't know properly - the teacher that made and maintains the school's website is probably stuck in 1998 judging by the design and functionality of the website and his clothes) and they then send absolutely clueless students to compete in a web design competition (and then they get angry at the judges for giving the students 0 points)