Have 1 or 2 "Plain Clothes" armed Security personnel in schools during school operational hours. Keep federal government out of it. Let States/Cities/Communities decide what is best for them and what they wish to fund.
Children will be advised security is present which should make them feel more safe and able to focus on education.
Security personnel should be former police officers or former military security type personnel (MP's/CID/NCIS).
Security personnel can be paid or volunteer depending on the schools budget.