Everything Under the Moon

Your mother can forbid rituals and tools in her house. She can't change what's in your heart. You can do your rituals mentally. Be patient with your mother.

Snow

Your mom may be fearing what she can't understand. Unfortunately some forbid what they can't understand instead of trying to learn about it. Is she of a particular religion herself?

If I've done my math correctly you are sixteen, correct?
Soon you'll be a legal adult, and hopefully you can move out on your own where she can't tell you what to do.

And SnowCat is right! She can't take away what is in your heart. She can't force you to believe or not believe.

Is there some sort of locked box you can keep your stuff in? Maybe chain it to a tree or bury it or something?

An altar can be as simple as a feather or air, a tealight for fire, a bowl of water for water, and a plant or bowl of earth to represent Earth. If you keep it nondescript it will be less likely to be noticed by would-be thieves.

You don't actually need tools, an altar, or elaborate rituals to be Wiccan. Spiritual paths are not created by the physical things you have or do, but by what you feel. Spent these two years reading, learning, and finding alternate means of connecting and celebrating your path.

Have you thought about getting a virtual altar? I don't know any sites off-hand, but I know they exist so a google search is in order if you are open to the idea. Basically, it's an altar you build on the internet that you can sit in front of during your meditations (or what have you).

One of the downsides of being Wiccan and living with parents or guardians is that they do have the final say on these matters. A parent's job is to do what they perceive is best, even if their children disagree. However, no one can take being Wiccan away from you. If you feel that you are Wiccan, then you will always be Wiccan until you decide to stop. That being said, I want you to know that even if you are practicing in secret, or even taking a break from practicing until you can do so freely, it doesn't make you any less Wiccan.
I would like to suggest that you pull together what material you can find on Wicca. Find examples of what Wicca is and what it isn't. Copy information from books and the internet. Keep track of any URLs when you visit websites or watch YouTube videos. Present your findings to your mom and try to have an open minded, civil discussion about why you feel like Wicca is right for you. Even if she still won't let you practice, at least she'll see that you're being serious and devoted to your path, and that it isn't some sort of whim or rebellion. At least you can say that you tried.
There are some things you can do that are Wiccan without spells and rituals. You can study Wicca. You can make things for any spirits you interact with. You can meditate. If you're good at visualization or are proficient with astral work, you can perform rituals in your mind or on the astral plane. You can grow and interact with plants. You can collect pretty rocks, crystals and minerals. Take joy in the world around you. Wicca isn't defined by just spells and rituals.
If you want to have an altar at home, you can look for things to put on it that aren't so obviously magickal tools. Why not draw pictures of the things you would want on your altar if you can have one out in the open? You could paint four rocks a different color for each of the elements. You could use angel statues to represent the four archangels that correspond to each element. You could make a necklace or bracelet with colored beads and charms to represent the elements and the Lord and Lady. You can use battery operated candles instead of real ones, and water mixed with a few drops of essential oil instead of incense.

Perhaps the best thing to do is to have a mature, serious talk with your mother. Ask her to come sit down with you when you won't be interupted, and very calmly explain to her what you would like, why it is not a bad thing, and that it is a part of you. Make sure you never raise your voice or get into a hostile body position, and also answer her questions. Act mature and usually you will be treated with respect. Make sure you understand your mother's opinion as well.
Best of luck,
-Elly