I realize I'm joining this late - however I wanted to add something that I don't think has been mentioned about T-coil reliant systems (versus "boot"/"shoe" systems)
One MAJOR drawback to T-coil based systems is that they are very dependant on the area in which they are being used - in some siuations they are WONDERFUL ... but in others they make listening situations WORSE than using nothing at all.
This is because depending on the environment (presents of CRT TVs, Computer Monitors, various types of common electrical equipment etc and
especially florescent lighting) they often have a HUGE amount of buzzing etc noise (sort of like electric hair clippers or something) that is present when the HA is in "T-Coil" mode.
Because schools tend to be lit exclusively with fluorescent lighting and often have misc electrical equipment in classrooms - this makes using anything T-Coil based an "iffy idea at best" .
I'd recommend using something that is DAI aka "direct audio input" instead - which means a "boot/shoe" based system.
Keep in mind that there are also different boots/shoes (same thing).
Some boots/shoes are set to have the mic ON while connected and in use (so the HA user can hear room sounds via the mic at the same time as they hear whatever they are listening to via the boot/shoe - while other boots/shoes switch the mic OFF while connected so that the only thing the user hears is what is being routed via the boot/shoe DAI input.... there are other boots/shoes that have the ability to do both via a tiny screw/switch adjustment (should be adjusted by an adult or once the user is a teen they can do it themselves if needed).
If this "dual" boot (one with an adjustment that allows you to have the mic on or off when connected) is available for the users HAs I'd think this would be the best option as it allows the user/parent to adjust the "listening environment" as needed to most benefit the user.
If the "adjustable" boot/shoe is NOT available - I would recommend having 2 "mic ON" boots/shoes and possibly one "mic off" boot/shoe. This is because for classroom etc listening it is important that the child can clearly hear the teacher (mic off shoe) however (depending on the HL) also be able to at least be aware of other children speaking if possible (mic on shoe). The ability to have one ear (for bilateral users) that is "JUST DAI" ie "just teacher" can be VERY helpful
If the person uses HAs bilaterally (both ears) then it may be a good option to have one boot (in their "worse ear" if applicable) that is a boot which is mic OFF when in place (so it's 100% DAI sounds, no mic/room sounds) ... and have the other (ear better for speech rec) have a DAI boot that is mic ON (allowing them to listen to room sounds AND the DAI boot/shoe sounds).
The other advantage of the DAI boots is that they are able to be connected to MP3 players, computer speakers, phones, TVs etc - which makes them very useful for both school and "everyday life" (and because many of the things are "fun things" even the youngest kids are less likely to "buck the idea" as the boots/shoes allow them to hear things they WANT easier too
)
P.S. for very young children - it would be a good idea to give them an easy yet specific way to explain "I can't hear right" "this sounds horrible etc" ... it could be as simple as having them POINT to the ear that is "broken" and shake their head etc... something that clearly says "something is wrong with THIS ear/HA" .
One easy way to teach even toddlers is to play (for short periods of time - say 1-3mins) a "HA on off game" - where one HA is turned off and they have to say which one changed (very easy to do if you have a remote).
Teaching children who wear HAs (or CI for that matter) from "day one" how to indicate their HA/CI is working or not can be very helpful - however it's something that (for some odd reason) not all audiologists suggest or show parents how to do.
One easy way to start is by have a gesture (even if you are not using ASL etc for language/communication) that means "I can't hear/understand" (such as point to both/one ear(s)& shake head "No") every time before the HAs are put on (and turned on) ... then once they are put on (and turned on) then the gesture becomes "I can hear/understand" (ie point to both ears and nod "yes") - then every time there is a change in hearing (ie HA/CI turned off/on or put on or removed from the user) the appropriate gesture ("yes" for working, "no" for not) is used by the adult/parent/etc as well as the HA/CI user (help them gesture if needed). After they've understood completely the "off" and "on" change , more subtle changes can be practised as well - for example flip the HA into T-Coil mode (without connecting to any T-Coil listening equipment/ loops etc) and gesture that the ear with the HA set to T-Coil is "not working properly"
Hope that helps!!