A System 9 (MacOS 9) bootable PowerPC Mac cannot / does not boot into 'Classic'; it boots into 'System 9.x'. When booted into 'System 9.x' - all of the capabilities of 'System 9.x' are available.
'Classic', when launched, from a MacOS X booted Mac - is a crippled version of the installed 'System 9.x'. When utilizing 'Classic' - not all of the capabilities of 'System 9.x' are available.
Also, once 'Classic' is launched (opened, run) and all 'System 9.x' related applications, in use, are finally quit'ed - the 'TruBlueEnvironment' process remains running - possibly reducing the overall Mac experience ... until via 'System Preferences' 'Classic' utility (or other means) 'Classic' is 'Stop'ed or 'Force Quit'ed.
MacOS X'es 'System Preferences' 'Accounts' utility's 'Login items' (
Tiger', or similar for earlier MacOS X versions) list has nothing to do with what OS the Mac will boot from. Such action is determined via 'System Preferences' 'Startup Disk' utility, or 'System 9.x's 'Startup Disk' control panel.
Via 'System 9.x's' 'Apple, Control Panels, Startup Disk' sub-menu item - locate and select the 'Mac OS X' to boot from, and restart the Mac.