sorry, i fixed it just after i posted this thread.
I totally forgot to declare the "School" element. this works:

<!ELEMENT personal (f:name,l:name,age,school)>
<!ELEMENT f:name (#PCDATA)>
<!ELEMENT l:name (#PCDATA)>
<!ELEMENT age (#PCDATA)>
<!ELEMENT school EMPTY>
<!ATTLIST school yr CDATA #REQUIRED
schl:name CDATA #REQUIRED>

thanx u people