Glue ear. It's not a Prittstick in the lughole. If you have children with permanent train tracks of snot coming out of their nose, even in the summer, maybe they have Glue Ear.
This last half term will speed by, but it's not too late to squeeze in a targeted 6-week programme to encourage the sounds they don't have yet.
Cued articulation is a visual support for the complete sound system. It is a series of signs to give a child more information about how to say their target sound, rather than them just looking at your mouth or hearing the sound.
It's quite common for children to have difficulty with "L" but it's quite an easy fix...