[DRIFT_HUNTER]

pawn Code:

new AllowedToSpawn[MAX_PLAYERS];

public OnPlayerRequestClass(playerid, classid)
{
    AllowedToSpawn[playerid] = 0;
    if(classid == 4 && PlayerInfo[playerid][pAdmin] < 1)
    {
        AllowedToSpawn[playerid] = 0;
        return 0;
    }
    return 1;
}

public OnPlayerRequestSpawn(playerid)
{
    if(AllowedToSpawn[playerid] == 0)
    {
        SendClientMessage(playerid,COLOR_GREEN,"You may not spawn.");
        return 0;
    }
    return 1;
}

OnPlayerConnect and disconnect add AllowedToSpawn[playerid] = 1;