HOW CAN I IMPROVE MY MAPS ?

Classrooms don't have windows behind the teacher anyway, the windows are on the sides or back of the classroom so that the sun is never shining in the student's eyes when they're trying to read the chalkboard.

That said, increasing the wall height to 3 tiles is probably your best bet if you really wanna put a window there.

Looks fine but that room could be cut in half. It's far too big. Look at the room you're 'copying'. It's as wide as two windows. For size's sake, make it big enough for three or four windows with no room between them. That should be plenty large enough for a table and side-cabinets.

Also, don't forget this:
Alright, so here are a few tips.
1 - Never underestimate the wall overlap technique. This makes your map look more realistic. You're looking at the map at a 3/4-ish view, so you won't be able to see what is directly behind the walls. Most walls are 2 tiles high, so there are 2 tiles worth of space behind them, hiding things from you.

2 - Shift Mapping. Holding Shift while placing auto tiles allows you to place the middle tile instead of the outer ones. This helps with edging issues, like with your carpets, how the design on the edges makes the carpet look like it's oddly cut. (Most carpets being square or rectangular.) Holding Shift while placing the carpet tile will make it look more like the red carpet has been thrown over the peach one.
The second part of Shift Mapping is this: When holding Shift you can copy an exact tile and if you hold Shift while placing it, it will remain the same. Shift+Right mouse click to copy, Shift+Left mouse click to place. This helps out a lot with autotile placement too.

3 - Learn how to conserve space. Give a rough estimate to your tiles and stick by them. I tend to think of tiles as equal to two steps. Others have different measurements. The deal is to make it consistent. Also, outsides vs inners. Make a concentrated effort to make them at least consistently the same size each time. (I like to make insides about 2x the sizes of the houses outer shell. It gives me room and helps when scaling all areas.)

4 - Don't decorate for decorations' sake. It's okay to break this rule sometimes, but putting pots and flowers and shit all over just to take up room means that you have too much room. If you're struggling to cover ground, or have 3 or more of the same decoration just to take up room, try cutting off a tile or two of space in your map.

5 - Keep in mind what the map is supposed to be and what is needed in it. Also, for inners, the people who live there and their personalities. If a Carpenter runs a shop inside his house he'll have carpentry tools around. If you have a sailor or fisherman they'll have fishing and sailing equipment indoors. If a bachelor, not likely to be flowers and cute stuff around.

6 - A bed for everyone! Or at least allude to it. If you have a house with a three person family, unless they are very, very close they won't just have one bed between them. You could have doors on walls that are locked or just won't open to show that there are other rooms to a house if you don't want to expand the inners too much, but remember the people who live in the house need to have places to sleep too.

7 - The outside =/= (DOES NOT EQUAL) the inside. If you're trying to make an outside that is the same size as your inside it will come off looking very dull and bad most of the time. (There are cases of this working, but not often and not likely with the RTP tiles.)

8 - Nature vs nurture. Nature is hectic, wild and untamed. The farther you go into lands that are unexplored, the less likely bushes, trees and flowers will line up in rows. Cliffs should not be unbroken lines, water should not be a long straight one-tile river, paths will not be just straight lines and grass does not grow in 3x3 clumps. Make things more random.
Whereas in towns you will usually find more structure. Gardens, while in some cases still a bit random, will usually be more carefully planned. Trees are found in rows, grass either mowed or cared for and streets run usually in straight lines.

A way to get better: Study/look at other maps in 2D commercial games. Not 3D games - they have more graphical shit to work with. Also, try to practice by recreating maps that you like in the maker. Experiment with things and find out what looks good and what doesn't.

The very best way to learn is to DO.

Also, asking for input is a great idea. Good job~

The ground tiles are perfect, I think, otherise, this room is longer than wide so cut it left and right (just put black tiles on each side, the one you find top left on the tileset with nothing on it), finally, maybe you could make the walls in this room slightly bigger by one or two tiles?

I dunno, LockeZ. If you take his current outside houses, his insides are gonna be a 4x3 width all up. That's with all rooms included. (Usually I double the size of the inner. That way it has a constant size per tile, but isn't so small on the inside that you can't move or have anything, or so large on the outside that you have to walk miles to get from house to house.)

I don't understand what you're saying Liberty, I'd move them up 1 tile as Mr_Detective says.

I dunno, right now it looks right to me, if you move them up one it will kinda look like the base is on the wall wouldn't it? As opposed to the floor in front of it?