Students at Maple Hill Elementary and Monhagen Middle Schools were on lockout and lockdown after district officials say a threat was called in Wednesday morning.
It was the second day in a row a threat had been called in.
The district has been plagued with nearly a dozen so-called "swatting" incidents since September, and frustrated parents say they are concerned for their kids.
Police have arrested a 9-year-old Middletown girl in connection with one of the bogus calls.
The FBI is investigating the other calls.