are you sure that 24K includes your housing and school fees? They are usually extra benefits...... an offer for some usually reads like this

an example....

basic salary = 20K
housing = provided by company or 15K
school fees - paid by company or 50% fees paid by co.
Transport = car provided or cash allowance of 2k
Medical = provided based on Qatar medical plan
Leave = 30 days per annum
Flight = flights for the family per annum Doha-London-Doha
gratuity = as per qatari labour law

did you get a similar breakdown?