Does punishment have to be HARSH to effective?

My mum is soft when it comes to discipline, when she grounds me, I sneak out, ( IT DOESN't DETER ME ) now my mum says if I sneak out again she will have no option but to lock me in my room so I CAN't sneak out, I will have to serve 1 weekend minimum lockdown, NO entertainment, my bedroom door will be kept LOCKED at All times ( except for bathroom ) my mum says a harsh punishment is required to deter me from sneaking out.

does punishment have to be harsh to be effective?

ps grounding does NOT deter me, lockdown is a punishment I FEAR the most I would hate being locked in all weekend

Troll.

Not necessarily. Punishment does not necessarily change behavior and a lot has to do with teaching moralities and respect. Minimal punishments can cause major changes, and maximum punishments may only cause increased bad behaviors. In general, children that are hit, learn violence as a solution to problems and they becomes less moral people in society.
In terms of dealing with children, the most effective is privileges rewarded for good behavior, and withholding and removing the privileges for bad behavior.

A Greek philosopher Epicurus, in about 300 BC over 2000 years ago, is attributed with:
"Riches do not exhilarate us so much with their possession as they torment us with their loss." - Epicurus
The worst punishment in modern society for a child, is AFTER rewarding him/her with an iPhone for example, to take it away as a punishment, yet, such a "punishment" of taking away a cellular phone, can hardly be viewed as severe.

In order to be punished effectively, one has to start with a reward system for good behavior, and hopefully both parent and child are in a position of respect for each other. It also should be in levels such that minor offenses have minimal punishment so major offenses are recognized as such.

For example, if punished to stay in your room for a time period, allowance for meals and restroom, and tack in writing an explanation of why the action done was improper would be a level.
[A simple first offense punishment - Go to your room. Think about what you have done. Come out when ready to sincerely apologize and mean it with a full explanation.]

If sneaking out, that is a total lack of respect and defiance and is completely unacceptable. The first event is a discussion of sending the child to a military camp or reform school because they don't belong in the household, and the second time it happens, that is where the child ends up.

Lockdown? I would never consider it. As far as I'm concerned there may be no door at all. If a child is not taught respect and honor of both himself/herself and others, both parent and child failed.

Things are great, until a child F's it up, and punishments go geometrically.
Add: A good one: Write out your own punishment - sign and date it, and include what happens if you do wrong during the punishment or violate the terms. We'll see how effective it is if there's ever a next time.]

In comments: "my mum has given me many chances to comply and I have ignored them"
Failure to properly communicate. Message never received.
"Good people do not need laws to tell them to act responsibly, while bad people will find a way around the laws."- Plato
You were never taught to respect her and act responsibly. The punishments are all useless to you.
That is something to think about. My parents never needed to punish me, because I never gave them cause to do so, and I had a total freedom growing up.

When soft punishment doesn't work, yes, it has to be harsh

It doesn't have to b harsh, but it DOES have to be punishment. By YOUR statements, you have not been punished.

Just a timeout… You think about it mister