Lots of school shortages in general. Not just teachers, but bus drivers and security officers too. Kids are getting home at like 8pm from school because there are so few people willing to drive school buses, and nobody wants to potentially get shot for a security guard salary.
Well, probably not so much an employee shortage as much as a good employer shortage. Because I'm sure these school districts absolutely shit on their employees at every turn and heap them with workloads of 3-4 other people while not raising their pay. The school district where I worked years ago runs help wanted ads damn near every week with multiple part-time and full-time job openings, and I know it's because administration sucks, pay sucks, and the union is absolutely worthless. They have very high staff turnover - meanwhile, the neighboring school district might run one help wanted ad a year for like a custodian or a lunch lady.
Last I knew, some school districts were getting desperate enough to let basically anyone teach, regardless of whether or not they have the proper education and credentials to be educators. Nobody wants to teach because all the teachers are tired of being treated like shit by parents, students, and administration. They're tired of being underpaid and overworked. They're tired of not being able to do anything with disruptive students or risking their lives any time they go into work because school shootings are becoming more frequent. It's bad when you see shit about former teachers working at WalMart or Target and being treated and paid far better than when they taught for a living.
Districts and breeders are reaping what they sow. After years and years of mistreating the people tasked with educating current and future generations, schools and parents are acting completely shocked when those educators get new jobs that are less stressful and abusive.