Of course you could “cheat”. Not tell them you moved… But there’s a risk of being caught. And the school district does send out mailings periodically – likes your kids’ CST scores, results of GATE testing, etc. You’d probably get busted when those bounced.
I’m not sure what the policy is if you have been in a school and move outside – but still within the boundary. It might vary by school. I know of one case where a student who’d grown up in the La Jolla schools was accepted at La Jolla HS after her parents moved out of SDUSD to Poway. (Out of district is a bigger hurdle than out of boundary but within district.) But she had to show strong ties – still active at La Jolla High because she participated in all sorts of school sponsored extra-curricular activities… strong ties to the community/school body, still super active in LJ Presbyterian youth program… In other words – she’d had 9-10 years of hanging with the same kids, doing the same activities when her mom and step dad rudely moved her outside of the district. So there are ways of getting exceptions made… but sometimes you have to work it.