I was positive beforehand that you could apply to a school ED if it wasn’t SCEA or early restrictive and then apply to as many other EA schools as well. However, one the admissions officers of Northwestern told us that it was highly unethical to do so.
Any disagreements/agreements?
Yes you can, I applied to UB EA and UAblany EA. apparently UB lost my application and had to send it again. I ended been a regular decision 
Each school seems to have a different policy, so read that policy carefully. Here is Cornell’s: http://admissions.cals.cornell.edu/apply/first-year/early-decision
Early decision at Cornell is a binding commitment. While you may apply to other, non-binding early admissions programs, you may only apply early decision to one school. Early decision means you have committed to enroll at Cornell if accepted, and you must withdraw any applications sent to other schools and send your acceptance deposit by the date specified in your acceptance letter.
I looked at Northwestern’s website and did not see where it prohibited any EA applications.
Note that some schools like Notre Dame prohibit an ED application at other schools if you want to apply to ND Early Action.
Bottom line: research the requirements of each of the schools where you will be applying.
I don’t see why it is unethical at all unless doing so is specifically prohibited by the ED school. You must decline the offer of any EA school if you are accepted to your ED school.
There is no guarantee of getting into the ED school so having some other schools that are EA or rolling could serve as a good safety for a student.
Here is what I know about it: all schools that are ED only allow 1 ED school (them) and no Restrictive Early Action, but you can apply to as many non-binding EA schools as you want and an ED school and if you got in to said ED school, then you would have to withdraw your application from the other EA/all other schools. For example, I’m applying early decision to UPenn, but I’m also applying EA to UChicago. If I get into Penn, I have to withdraw the UChicago application. By the way, for the most part it is only Jesuit schools that don’t allow this (e.g. Notre Dame, Boston College, Georgetown (possibly Villanova)). You couldn’t for example apply ED to Penn and EA to Georgetown. I hope this helps.
As long as the ED school allows you to apply early elsewhere, it’s no problem. In fact, it’s very common. My oldest applied ED to brown, EA to Michigan, uchicago, rolling to Pitt. Youngest applied ED to brown, EA to Michigan & Tulane, and rolling to Pitt and Wisconsin. He later applied Ed2 to tufts.
I applied ED to Northwestern last year while applying to a few through EA and will be attending Northwestern this fall. Just make sure to check if the colleges you’re applying to EA allows you to apply there while also applying ED to another school. Also, if you do get into Northwestern, make sure to tell the schools you got in through EA that you won’t be attending. Good luck!
Read (and follow) the rules for the schools you’re actually applying to. Simple. My D applied to Pomona ED. She was going to also apply to Georgetown EA, but realized that the rules on the Georgetown website don’t permit this.
Some ED schools may only allow you to apply EA to public colleges.
Most ED schools don’t prohibit applications elsewhere. They expect you to join them if admitted ED and give up all other schools.
All SCEA schools prohibit ED or EA to schools but make exceptions for publics.
Most EA schools don’t care what else you do since they expect you to follow the rules of other places you are applying to. Exception that I have seen is Georgetown which would prefer you not apply to them if you are doing ED anywhere.