What causes battery drain on MacBook Pro in sleep mode?

That computer is a battery-CAPABLE device. It is not optimized as a battery-operated device. (It is NOT an iPhone.)

Your computer performs best when connected to AC power, such as the power adapter. It can use the full output of the Power Adapter AND when doing especially challenging work will also freely "borrow" power from the battery. In some cases, even with the power adapter connected, the charged state may decline during very stressful work.

When used only on battery, your computer has no extra cushion of power, and may perform more slowly. However, for ordinary non-stressful tasks this may not be objectionable (possibly not even noticeable.)

In general, you should ALWAYS connect a power source when it is possible to do so, and only run on batteries (which could be somewhat slower) when no power sources are at hand. Modern Macs maintains optimum battery charge levels under program control, and will NEVER over-charge. Activate Battery Health Management and do not spend another moment of your time thinking about charging.

That blocky device that plugs into the wall is the POWER ADAPTER. I am not trying to be a jerk about terminology, what these boxes do and how they do it is essential for understanding how they all work together. The LEDs in the MagSafe end are controlled by commands from the computer.

Connected to Power is NOT necessarily charging.

The CHARGER is inside the MacBook Pro, and is completely under program control. Your Mac accepts some power when needs to run, and accepts more power when intends to charge its internal battery. A power source like the Power Adapter or certain Displays can not 'force itself' on your MacBook Pro. Only the algorithms inside your Mac can decide when is a good time to charge the battery. Your Mac can NEVER be over-charged.

As I tried to say, plug it in when you set it down. Then you won't CARE whether it would drain the battery when nominally asleep.

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The most common issue users are experiencing is, that when they close the lid, their MacBook Pro does Not sleep, and if they want to know about that in detail, they need to investigate Why.

Start by checking Whether it sleeps:

With the cover OPEN, touch the CapsLock key so that it light up. This will be your makeshift "sleep indicator".

Then choose "Sleep" off the Apple menu, leave the cover open, and do not touch anything else.

Watch the indicator light. At the moment your Mac actually sleeps, it will turn off that indicator. Wait a few minutes more and see if it stays asleep.

Let readers know what you find out.

<< recent drain while using in class (so on battery). >>

That part is likely a different (but possibly related) issue.

By far the easiest way to cause poor performance, instability, overheating and crashing is to install ANY third-party speeder-uppers, Cleaners, Optimizers, or Virus scanners, Bit Torrent, or a VPN that you installed yourself.

also, Consider downloading and running this little "discovery" utility, Etrecheck. It changes NOTHING. Etrecheck was developed by a senior contributor here, and uses mostly system calls and simple tests to collect often-needed information.

it contains little tests for speeds of devices, CPU utilization, memory usage, energy usage and a digest of recent problems, in one easy to use package. it does not even need to be Installed. Because less can be learned when your Mac is running great, best time to run is when your problems are actually occurring, if possible.

if you follow the directions faithfully, its report (pre-laundered of all personally-identifiable information) can be "Shared" to the System ClipBoard, then Pasted into an ‘Additional Text’ window in a reply on the forums.

Use Etrecheck Pro for free:

http://Etrecheck.com

The amount of data you get can be daunting. If you POST your report, some Readers here are willing to look over those reports, and can provide valuable insights.

The start a reply on the forums, click the "additional text" Icon, and PASTE

what is the date of your most recent backup, and by what method?

You ran Etrecheck under an non-Admin account, so it could not report your backup drive or any kernel panic reports.

at only 37 GB drive space FREE, your drive is full, and this may cause MANY weird things to start happening. the standard is 20 percent should be free, about 50 GB for a 250 drive.

There are many more things to say about your current report when you get those items under control.

"On the cloud" is great for sharing photos, but is not a viable backup solution for everything you have. The stuff is not under your control, and is subject to sloppy handling, arbitrary changes in policy, theft, accidental deletion, data loss [are they making frequent backups using best practices?], and discontinuation or throttling of the service. It can easily take three days to restore it at ordinary Internet speeds.

If you do not have a recent local, disk-based backup, your computer is like a ticking Time bomb. You are only one disk failure, one mainboard failure, one crazy software, or one "oops" away from losing EVERYTHING! Drives do not last forever. It is not a question of IF it will fail, only WHEN it will fail. In addition, you never know when crazy software or Pilot Error throws away far more than you intended.

If you are using another direct-to-disk backup method that you prefer, and you currently have a recent disk-based backup, that is great. If not, you should consider using Built-in Time Machine. Take steps to acquire an external drive as soon as possible. If you buy one, a drive 2 to 3 times or larger than your boot drive is preferable for long term trouble-free operation. Do not pay extra for a drive that is fast.  (You can get by for a while with a "found" smaller drive if necessary, but it will eventually become annoying).

Attach your external drive and use

Settings > General > Time machine ...

... to turn on Time Machine and specify what drive to store your Backups on.  It may ask to initialize the new drive, and that is as expected. APFS format is default format if running MacOS 11 Big Sur or later.

Time machine works quietly and automatically in the background, without interrupting your regular work, and only saves the incremental changes (after the first full backup). Time machine backs up your machine — including every connected drive that is in a Mac compatible format. it can not back up Windows format drives.

Time Machine's "claim to fame" is that it is the backup that gets done. It does not ruin performance of the rest of the computer while doing its backup operations. You do not have to set aside a "Special Time" when you only do backups. When you need it, your Time machine Backup is much more likely to be there.

How to use Time Machine to Backup or Restore your Mac:

Back up your Mac with Time Machine - Apple Support

NOW is a great time to make that backup. Especially since you may have problems that require an ERASE and re-install.

If you need to submit your Mac for service, they make you affirm that you have All the backups of your files you want, and OFTEN erase/replace the drive.

also, can you re-run an Etrecheck report as an Admin?

The good news:

The diagnostic information shows only ordinary annoyances, such as high CPU use, no panics, and no smoking guns.

That is the ONLY good news in your new report.

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Your drive space situation is even more desperate than before. Only about 9 GB free space. You are in danger of completely filling your drive, which could cause a spectacular deadlock or crash, possibly including data loss.

Your computer has only 8 GB of Real RAM. That means the extra required to do your work is being simulated on the boot drive. Your swap file has grown to 130 MB.

To run MacOS Ventura or later in an appropriately-responsive way, you need to have MORE than 8GB or RAM installed. Otherwise you will be limited to running ONE application at a time, and quitting your browser whenever you want to do anything else. Also restarting several times a day will required.

The computer you bought, with 8 GB RAM and a very small 256 GB drive was intended for elementary school students who are storing everything on other devices, and are never expecting to use Microsoft Office apps, Music apps, or anything consequential.

Such completely under-resourced configurations are no longer sold by Apple for ANY purposes. Minimum RAM sold now is 16 GB on any Mac.

Unless you are willing to run one-App-at-a-time, Quit your browser to run Anything else, Restart multiple times a day, and find a way to dramatically reduce the number of files you are keeping on your boot drive, you need to REPLACE that computer with a better one.

Your existing computer may have trade-in value. You can check by going through the motions using the link below. You can easily exit the process long before you commit to actually trading in.

Trade in. Upgrade. Save. With apple trade in program.

NB>> if my colleagues strongly disagree with this opinion, I am certain there will be a Pig-Pile of dissenting opinions here very soon, typically within 24 hours.

<< drain while using in class (so on battery) ? >>

Running more than ONE app at a time in class will cause this. You must close all but ONE app to use this computer in an appropriately-responsive way.

Since the real RAM memory is so small, more than one App at a time forces the drive to run all the time, because the additional RAM required is being simulated on the drive. And because the drive is nearly full, writing takes a long time and everything slows. It also may hang from time to time waiting for the writes to complete, but this could be on a scale of milliseconds, so may not be noticeable.

Normally, if you had enough RAM and enough free space on the drive, the drive could stay unpowered most of the time. And battery would last far longer.

The usage you describe is normal. No actions are justified. As far as additional suggestions and recommendations go, read Batteries - Maximizing Performance - Apple.