Even if the school can’t change classes, have they increased supervision for both DC?
Many pupils in ASD special schools will have co-morbidities, including ADHD, dyslexia, DCD and anxiety. For someone whose primary need is ASD, ASD schools should still be able to meet needs. What support, including therapies, is in the EHCP currently and is it being provided?
Have you looked in neighbouring LAs, including independent and non-maintained options that are within travelling distance (typically considered 45 mins at primary, although some travel further)? If you post on MN, someone may have a suggestion.
If you want to look elsewhere in England, you could look at Alderwasley Hall school in Derbyshire, some of Cavendish’s special schools (e.g. Chelsea Hall in Wandsworth, Holmewood in Barnet, Hardwick House in Leicestershire, Heathermount in Berkshire), Hillingdon Manor in Hillingdon, The Rise in Hounslow, Unsted Park in Surrey.
However, what you describe covers a wide range of needs, so they won’t all be suitable. All have DC who display dysregulated behaviour at times. That is the nature of most special schools. But they don’t have the level of VCB the majority of SEMH schools have. Some of the above don’t take until Y3, but if DS is Y2 now, realistically you are looking at Y3, anyway.
If ASD specific schools won’t admit, you could look at somewhere like Brantridge and Muntham House both in West Sussex, Wilds Lodge in Rutland. All have DC with SEMH as well as ASD. Gretton in Cambridgeshire is an ASD school but has DC with SEMH needs in addition.
Personally, I wouldn’t EHE. If it is inappropriate for provision to be made in a school, I would look at EOTAS/EOTIS.