different term of Grade in IS

Dear all parents,

would like to know what is the diff. of grades between different International school are called :-

In SIS : they called from Preparatory Year 1, 2, Primary 1 to 6.

In AIS or ICS: They called from Receiption 1, 2 , Primary 1 to grade 5.

IN ESF : they called from Year 1 ... etc

any comment is highly appreciated.