I suggest looking for a behavioral therapy clinic. Most large medical centers will have them (it may be a drive depending upon where you live). They gave us great strategies and we are rarely yelling anymore (which was getting pretty bad). Some keys we took away were 1. Each parent spends time with the child (~15) mins a day where the child chooses the activity, parent narrates play and praises the child. 2. Throughout the day you give 3 x the positive comments vs the 1 x commands. Ex: "I like how you're sitting quietly at the table x" ... and 2 other comments similar about their good behavior (no matter how brief the behavior). 3. Use Active Ignoring techniques, by giving them praise frequently you're giving them a spotlight. When they are making odd noises, yelling, shrieking etc physically remove your gaze of them, completely ignore them. 4. Give 1 command at a time and be firm, do not ask it as a question. I.E. "I need you to get your shoes and put them on" instead of "Can you please go get your shoes on?". By saying the command like a question the kid things they have an option to NOT go get their shoes, telling them in a simple command is more effective. There are other techniques but these were the key 4 that we still use frequently.

A couple things to note: Try each technique consistently for 1-2 weeks (don't stop). Add a new one every 1-2 weeks, keep doing them so they become your new routine. Kids behavior will often get WORSE before it gets better mostly due to you changing up your discipline routine so they realize their old tricks for attention aren't working so they will act up more. Don't let that dissuade you, keep using the techniques. Also, praise them frequently most people don't realize how many commands they give their kids in a day (we didn't). The goal is to ramp up positive interactions instead of negative ones.

Lastly, after you find which of the above techniques work for you share them with your children's care/school providers that way they know what does /does not work.