if your using parameter then you need to add all in your string. then you can find "All" in parameter.
"Is there any way that I can set up these two global 'Parameter' filters to be related with each other? for example, when I pick one teacher in the teacher 'Parameter' filter, only the students taught by this teacher show up in the second filter's drop down menu? For now, no matter which teacher I choose in the first filter, all students names show up as options for the second filter which is really confusing for the end users."
For the above question you need to see this post:"Add to Context" Parameter Filters
You have to understand the order of operations how filters will work. that will help you to solve your problem.
Please have a look at this post :Cascading Quick Filters in Tableau - The Information Lab
Is it possible for you to join your data so you have one data source. In this way you would be able to use quick filters, relevant values, and even more importantly, as your data changes and new teachers and/or students are added, they would update dynamically. One drawback to parameters currently, is that they are not dynamic.
It does not make sense to join my data sources since they are on totally different levels.
I actually found a 3 year old post asking about the same question (link: "Add to Context" Parameter Filters ), but unfortunately, it does't seem to be solved.
Thanks for your response. Yes I can add "all" in my parameter string to make it show up in my parameter drop down menu, but do you have any suggestions how I could pass the "all" value to the corresponding calculated field, which I am using it as the True/False filter in my Viz?
Again, I am trying to use parameters as filters in a dashboard combining different data sources. When I set up the parameter, I am using the following logic for the corresponding calculated field, and then using this calculated filed as a True/False filter. In this way, how could I pass the 'all' value to this logical calculated filed? Any thoughts?
Please look at this post. this will help you.Adding "All" Option to Parameters
[Parameter] = 'All'
, [Parameter] = [Your Dimension]
[Parameter] = Number outside of you dataset. See Below.
, [Parameter] = [Your Measure]
This is a simple mockup calculated filed:
if [parameter name]=[Filed name ] then "Show" elseif [parameter name]="all" then "Show" else "Filter" end.
one more link:
If it solved your query mark it as correct . so that it will be easy to find the solution.