Pay attention at the back of the class, do your homework and know the laws of your profession.
As much as I sympathise with Aston Villa over Bernardo Silva's opening goal for Manchester City on Wednesday night, it was a fair cop.
The law, as it stands, is a nonsense and I can understand Villa manager Dean Smith's frustration before he was sent from the dugout for speaking his mind too forcibly after his side's 2-0 defeat.
But it was applied correctly by referee Jon Moss, and if Villa must look closer to home if they want to apportion blame.
First things first: Villa played their part in a cracking game, and how it remained goalless at both ends for nearly 80 minutes, I'll never know.
But every season, before a ball is kicked, referees hold seminars at every Premier League club to discuss changes in the law with managers and players.
And in the Championship, every club attends a meeting with the Professional Game Match Officials Board, where any tweaks to the laws are delivered to managers or their representatives.
The law governing the incident where Rodri ran back from an offside position to rob Tyrone Mings and feed Silva to fire City in front was amended four years ago.
It's not something that was sneaked into the smallprint at Christmas. It's been there, in black and white, since 2017 (when Villa were in the Championship).
As a professional footballer, it's part of your job to know the laws.
Just as a bus driver can't plead ignorance if he exceeds the speed limit, footballers need to know where they stand.
For the avoidance of doubt, here is the law Moss applied correctly: “A player in an offside position receiving the ball from an opponent who deliberately plays the ball is not considered to have gained an advantage.”
Once Tyrone Mings had chested the ball – a deliberate action – Rodri, who stole the ball off him after running back from an offside position, was not considered to be gaining an advantage according to the laws.
Yes, I agree with Villa fans who think the law's an ass. I think some of the laws governing handball are nonsense, too. And don't get me started on VAR.
But if players or managers don't know the law as it stands, sorry: It's your fault.
From my experience as a Premier League player, the attention span of 25 to 30 players in a meeting room at those pre-season seminars can be a little bit short.
I'm not saying they are as unruly as the back of a school bus, but when players are presented with new laws, they are expected to absorb them.
Do your homework, learn your lines, pay attention. This is your day job.
Apprentices at academies have to learn the laws as part of their scholarships. Some of Villa's players would have come through that system, so they have no excuses.
The same applies to pundits like me. If we are going to pontificate on aspects of the game, we need to make sure we're clued up on relevant changes to the laws.
Ex-players who tweet garbage – some of it provocative and quickly deleted – have a responsibility to the game and their colleagues in the media, too.
Villa have been a revelation this season, a breath of fresh air after their close shave with relegation six months ago.
But I'm sorry: It was a goal, and Dean Smith was wrong to complain about it. According to the law, Rodri was onside – fact.
And while we're dealing in facts, you can argue Villa wouldn't even have survived in the Premier League last July if goal-line technology had not spared them when the ball had clearly crossed the line against Sheffield United in Project Restart's first game.
The point they took from that game made the difference between staying up and going down.
I don't remember Villa fans complaining too loud about that one.
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