Prova così:

codice:
<%@ language= VBScript

option explicit
<% 
dim sql,conn,rs,x, User, Psw , rs2, sql2 

User = request.Form ("User") 
Psw = request.form ("Psw") 
%> 
<html> 
<head> 
<title> Visulizzazione Assenze e ritardi </title> 
</head> 
<body> 
<% 
set conn=server.createobject("adodb.connection") 
conn.Provider="Microsoft.Jet.OLEDB.4.0" 
conn.open(server.mappath("prova.mdb")) 

set rs=Server.CreateObject("ADODB.Recordset") 

sql=" select* from Studenti" 
rs.open sql,conn 

if rs("User")=User and rs("psw")= psw then 
	If Not rs.eof then 
		set rs2 = Server.CreateObject("ADODB.Recordset") 
		Do while Not rs.eof 
			sql2 = "select * from Movimenti,Studenti where '" & rs("User") & "' = '" & User & "' and '" & rs("psw") & "' = '" & psw & "'" 
			rs2.open sql2,conn
			
			If Not rs2.eof then
				Do while Not rs2.eof 			
%>
					<table border="3" width="100%"> 
					<tr> 
					<% 
					for each x in rs2.fields 
					    response.write("<th>"& x.name & "</th>") 
					next
					%> 
					</tr> 
					<tr> 
					<%
					for each x in rs2.fields 
					    response.write("<td>" & x.value & "</td>") 
					next 
					%> 
					</tr> 
					</table> 
<%		
					rs2.movenext
				Loop
			End If
		Loop 
		rs2.open sql2,conn 
		rs2.movenext 
	end if 

else
%> 
	<h4>User o password errati</h4> 
	Torna alla pagina di login 
<%
end if 
rs.close 
set rs = nothing 
conn.close 
set conn = nothing 
%> 
</body> 
</html>