It sounds as of you're being asked to do an awful lot on your own! Over here, we have what are called 'Teaching Assistants' in Primary (Grade/Middle) schools and Learning Support Assistants in Secondary (High) schools. My daughter was a Teaching Assistant in Primary for many years and is now a Parent Governor at my younger granddaughters' school due to that experience.

You sound as if you could use a couple of Learning Support Assistants! They mostly work one-to-one or in small groups with struggling students. Some are qualified in SEN (Special Educational Needs) support, some are bilingual. Higher-Level Teaching Assistants are able to lead classes if needed (if you're off sick, for instance). They also help with preparation, tidying up, managing class behaviour and admin tasks.

Of course, this became necessary when the Government forced Local Education Authorities to close down local Secondary Schools and create massive Comprehensive Schools, pushing class sizes from an average 15-20 to 30+. Note that this was not an economy measure, but a piece of social engineering meant to ensure that all social classes were present in schools on equal terms. It was contemporaneous with the abolition of other useful practices such as streaming, setting, single-sex education and the cane!