This is gonna be long, but I think it might really help you!
My kids (7, 6, and 5 - all girls) are pretty good about not mistreating their toys, but boy do we have issues with them cleaning up after themselves!! And they are all Montessori kids! Jeez. :/
Anyway, we have been doing PCIT (Parent/Child Interaction Therapy) with our 7 year old (mostly for her anxiety, not discipline problems), but they have a really great method of discipline. They call it "the perfect time out" and even though I am not a fan of the time out method, this has REALLY worked for our kids. 9 out of 10 times we do not have to give them a time out. :D
"For younger children a timeout is very effective and avoids other types of corporal punishment. It is important to follow a specific sequence in giving a timeout. The timeout that we teach parents in PCIT gives children a 'choice' to comply and provides ample time for them to make a decision."
PERFECT TIME OUT (every child no matter what their age should be given a 3 minute time out. PCIT has found that giving a 7 year old 7 minutes in time out is not necessary to be effective):
Parent: Please give me the yellow lego.
Parent: One, two, three, four, five. (counting should be done exactly the same way every time. Don't drag it out...simply count the seconds away.) You have two choices; either give me the lego, or go to timeout. One, two, three, four, five.
Parent: You didn't mind me. (Stand up immediately and take the child to the timeout chair/spot). You sit here quietly until I tell you to get up.
Child: (sits quietly)
Parent: Are you ready to come back to the table and give me the yellow lego?
Parent: (Child returns to the table with NO FURTHER DISCUSSION, parent ONLY points to the yellow lego - NO VOICE COMMAND)
Parent: Thank you. (do not use any enthusiasm here. JUST a simple thank you) Now please put the green lego in the container.
Parent: Thank you for putting the green lego in the container. I like it when you mind me right away (can provide a hug.) When you mind me, you don't have to sit in timeout (this is a KEY sentence to tell the child!!!!). Use enthusiasm here for compliance.
The most important part of the timeout sequence that parents often forget to do is to make sure that the child complies to your initial command after coming out of timeout. However, in PCIT it is the child's willingness to comply that we want. So, in PCIT, the child remains in the timeout chair until they are calm. It is then that they are asked whether they are ready to comply with the command. When practicing timeout in clinic we also give a follow-up command that requires your child to immediately comply. This is to make sure that your child truly understands that they can avoid a timeout by complying right away to your command.
REMOVAL OF PRIVILEGES
Removal of privilege begins with making a list of the child's favorite treats or favorite things to do. When your child does not comply to a directive you can begin to remove his or her most favorite things until they willingly agree to comply. removal of privileges is very effective as long as the privilege was something that was very important to them. Follow the same specific sequences in timeout; giving two choices and allowing time to comply.
It is important that you are predictable and consistent in removing privileges as a consequence. If you have told your child that they will lose their privilege when they get home from the park, or store, then you must follow through. So, you may go through a list of removing his or her most favorite things before you get compliance. If you follow through enough times your child will begin to believe that you will, in fact, take away those things.
Tone of voice is neutral!!!! Parents often say that they have to raise their voice to have children hear their command. Repeatedly giving commands in a very loud voice can be stressful to parents, and it often leads parents to being frustrated and irritated with their child. Some parents think their child is 'hard of hearing', when in reality their child has learned to tune them out. Give all commands in a firm and matter-of-fact manner, avoiding angry, frustrated, pleading, or loud tones.
RESPECTFUL AND POLITE:
Starting most instructions with the word "please" is respectful and provides an example of using good manners.
BE SPECIFIC WITH YOUR COMMANDS:
Make commands specific rather than vague. It is important to tell your child exactly what you want him/her to do. Providing a child with a specific command likely will result in getting the desired behavior. For example, instead of saying, "Please clean your room," a parent could say: "Please put your lego's in the bin" and "Please put the books back on the shelf" or "Please walk beside me".
EVERY COMMAND POSITIVELY STATED:
Avoid using No-Don't-Stop-Quit-or Not. These words are a subtle form of criticism and may cause some children to respond negatively, doing exactly what you've told them not to do. Instead, provide a command that is instructive and tells the child what TO DO rather than what NOT TO DO. For example, many children enjoy jumping on the couch or their beds. A common response would be to tell the child to "Stop jumping on the bed," or "quit it." A positively stated command would be, "Please sit on the couch.", "Please put your feet on the ground." or "Please jump up and down on the ground."
Hope that helps a little!! We have been doing most of this in our house since they were little, but started doing the time out's the way PCIT has taught and it is AMAZING how compliant our kids are these days!!!! I think you could totally use this with a child who is not taking care of their toys. "You have two choices, be gentle with your toys or I take them away for good." Eventually when they have nothing to play with they will get the message that you are serious.