Just got a job at a big ed tech company for the summer, have no plans of leaving, but worried about the confidentiality agreement

Just cross out any parts you don't like and initial them. They probably won't even look, but if they do, justify them as being unreasonable for your continued employability.

IANAL

There are several ways to go, none of them perfect. I'd recommend Stealth Mode.

Get a separate computer and do all of your work there.
Do not connect your mobile device to the company network
Do not work on company time
Do not talk about your side project, and don't put your name to it anywhere
Do not invite co-workers to comment, view or work on this project in any way.
Redline the contract and remove anything offending

The reason I'd recommend this is:

- Your idea might not work out and it'd be better for you if nobody knew. (Chance of this: HIGH)

- Some people at startups are doing the same thing, nobody wants it shoved in their face and they get annoyed if they are working hard and you are split

- A lot of non-compete stuff isn't enforceable anyway but you won't find out until it hits the courts

- Most startups don't have time to fight these legal battles so they might just let it go

- If they don't let it go, it probably means your project is working, in which case you'll probably just settle.