Unaccompanied Refugee Seeking Children
Leave granted from 1st April 2007 lasts until the sooner of 3 years (12 months from some countries) or reaching age 17 and a half. For decisions prior to this date it was aged 18 years or 3 years' leave.
But if they were granted Discretionary Leave (eg on medical ground) the leave is likely to be much less, probably 12 months.
What about Syrians?
If a Syrian applies for housing they will probably have been accepted as a refugee- most are given humanitarian protection status for an initial 5 year period so will be eligible for social housing and for Universal Credit / other benefits, and allowed to work in the UK.
Many will have entered through the Syrian Vulnerable Persons Programme which targets support for those refugees “at greatest risk”, where “evacuation from the region is the only option”, particularly survivors of torture and violence, or women and children who need medical care.
Under the programme individuals are provided with housing and specialist support to help them access education, the job market and mainstream services. A ‘fast track’ system is available for Syrians resettled through the VPRP, to allocate an NI number and ensure benefits are paid as swiftly as possible
However you cannot assume that just because they are Syrian that they have refugee status so you will need to check to see if their biometric residence permit / passport / other document states that they have refugee status, humanitarian protection or any other leave to remain. See above..