JonSnow is correct, DfE guidelines now state that LAC should be placed in schools rated 1 or 2 by Ofsted, except in exceptional circumstances. Of course, this does not mean a LAC should be removed from a school they are happy and settled in just because it receives a poor Ofsted report, but SWs and Virtual heads have a responsibility to ensure that education is given the highest priority when children are placed.
TeenandnTween is also correct about faith schools- they must have LAC and former LAC of the faith (this can mean having been baptised within a certain timeframe, or attending a particular church for a certain amount of time) as the highest priority, and can place LAC not of the faith below all other children of the faith, but above other children not of the faith.
LAC and children adopted from care are excepted children and do not count towards Infant Class Size regulations. In practice, this means that a school can accept a LAC or adopted child even if they are full- many admissions authorities don't properly understand this, and refuse a place at a particular school because 'it is full'. The legislation was brought in to address this- LAC are far more likely to need a school place mid-year and all the good schools are full; which, in many areas, led to LAC only being given places in schools which nobody wanted.
If your child is still in care and the chosen school refuses to admit them, then the LEA can move to direct them to do so. If it is an academy, the Secretary of State has the power to do so.
Find the school you think is best for your child- this should be the only consideration.